If you believe your wife will have trouble managing finances, or will be tempted to dramatically change course, the Vanguard Personal Advisor Services is cheap (0.30% / year), and may make her feel more secure as there will be somebody to talk to, and who is paid to look at it. 2055 target fund may be tempting to change over time, perhaps not into the wisest alternative.
Also, respect from afar for being a good husband and taking care of your family. Best wishes for time, and happy time, with them.