I'm probably in as good of a position to answer this question as anyone. My wife is a physician and I'm a public HS teacher in TX. So we have a comparable income. We moved here from the west coast for her residency so aren't really *from* Texas and don't have roots in any specific place but have been here long enough (over 10 years) to get a feel for the place.
First, airports. DFW is by far the best airport in Texas for the frequent long distance flyer (i.e. not short Southwest flights) because it is decentralized meaning you can pretty much drive right up to your gate and there are mini security screening locations all over. So it is great for the business traveler departing to and from DFW. I've flown infrequently through IAH and always seems to take longer due to the terminal design funneling everyone through the same security screening location which gets jammed up. But that was a few years ago. Austin and San Antonio are really regional airports but they may work just fine depending on what your normal flights are. For example, Austin has a daily Southwest non-stop to Portland which we have used and a daily Jet Blue and Southwest non-stop to NYC. Hint...google is great for finding flights. Just google "nonstop flight austin to NYC" or whatever and they all pop up. And then Dallas and Houston both have secondary airports with lots of regional Southwest flights.
Regarding suburbs. All the major cities in TX (and even the minor cities) are going to have exactly the kind of conservative suburbs you are looking for dominated by tidy master-planned and gated communities full of $300-$500 grand houses built by the same regional or national builders. Houston suburbs will be more green with bigger trees and more water features. Dallas will be more prairie. Austin and San Antonio will be more hilly with limestone bluffs and more dramatic scenery. But the houses and schools will be pretty indistinguishable for the most part.
As far as schools go, with few exceptions, the average income of the community will determine the school quality (AT LEAST AS MEASURED BY STANDARDIZED TESTING) and that is mostly because the wealthy communities lop off the bottom tier of students by exclusive housing policies, not because the top levels of the schools are necessarily better. In other words, School A and School B might have exactly the same top-25% of the school taking the same AP classes and going to the same colleges at the same rate but school B's district covers a more diverse area drawing some students from lower socio-economic levels and from more diverse ethnicities. School B will almost certainly have lower ratings because the state ranks schools based on the performance of every ethnic and socio-economic subpopulation and if, for example, a small number of one group don't pass the standardized tests at the same rates as the wealthy white kids the schools rating is downgraded. However the schools from exclusively wealthy suburbs never face this because they basically have no poor or minority kids at all and end up with higher rankings that they don't necessarily deserve.
So where to look? Most people in your friend's position will look at:
First, the northern suburbs of the DFW area. The highest end suburb would be Southlake which has schools that always seem to win everything from academic to athletic competitions at the state level. The main high school ranking in Texas is called the Lone Star Cup which is the compilation of all the athletic and academic competitions. Here are the 2013-14 final rankings:
http://www.uiltexas.org/press-releases/ ... -announced Eight of the 11 schools on the list are from the northern DFW suburbs, one is from San Antonio and two are from the Houston area. In addition to Southlake there is Coppell next door which is slightly more affordable but still very upscale and the somewhat older city of Grapevine which I like a lot because it isn't so brand new and master-planned. They all have great schools and nice neighborhoods. The Keller area over closer to Fort Worth is also popular. And there are lots of suburbs further north including Allen and McKinney that are very popular. Most people with small kids will not move into Fort Worth or Dallas proper due to the schools unless they were planning to send their kids to private schools but that is a whole different level of wealth. Except for Highland Park or University Park in north Dallas which are separate cities around the SMU campus that are very very upscale and have their own small and exclusive school district. That is likely to be way out of your price range.
In the Houston area there is the Woodlands which has been mentioned here numerous times. It is a MASSIVE unincorporated master-planned community north of Houston and close to IAH. I think something like close to 100,000 people live in the Woodlands so it is overwhelmingly large compared to typical suburbs in other cities. How close you are to the airport would depend on which side of the Woodlands you live on. My wife and I have visited several times and looked at houses. It has a lot to offer. The Katy area west of Houston is equally popular and has similar subdivisions. We have friends who live in the Cinco Ranch master planned community which is massive and similar to the Woodlands but with less pines as it was once a prairie. You are much further from the airport though which would be the one drawback. Sugar land is also popular to the southwest of Houston as is Pearland and Friendswood to the south. But you are definitely in the Gulf Coast humid climate down there.
In the Austin area the choice suburbs are all in the hills west and northwest of Austin. The Lake Travis area and the Westlake area will be the two top choices out there. The terrain is much hillier and really quite pretty with lots of views that you won't get elsewhere in TX except perhaps El Paso. Both the Lake Travis and Westlake area have highly rated schools and lots of upscale housing developments. The one drawback is that the Austin airport is on the far eastern edge of the city so it will be a bit of a hassle to get to from the far western suburbs. Google maps can give you pretty good drive time estimates and distances.
In the San Antonio area most people will look at the northwest suburbs along I-10 and 281. There are lots of options including Boerne which is out I-10 and places further in such as Shavano Park which is a wealthy enclave within the city of San Antonio and might be out of your price range. I go jogging there every time we visit relatives in San Antonio and it is gorgeous.
As for the heat? Well, one does adjust. We moved here from Alaska and the Pacific Northwest and it took a while. Everything in TX is air conditioned and you basically have your 3-4 months of the year when you spend most of your time in a climate controlled environment just like most other places in the US except that here it is the summer not the winter. The Houston area would definitely be the biggest adjustment due to the Gulf Coast humidity but everywhere in TX is going to be something of an adjustment.
EDIT: After this long post I realized I didn't give any specific recommendations. If I had to recommend one single place based on the OP's criteria I think I would recommend Lakeway/Lake Travis area west of Austin. Very pretty, great schools, lots of good housing and neighborhood options and there is the lake although the past couple of years the water level has been WAY WAY down due to the drought. I was just down there last weekend for a HS football game and both the schools and surrounding community is really attractive
http://www.realtyaustin.com/schools/lake-travis-isd.php
http://www.laketravisisdhomes.com/neighborhoods.php