A few more thoughts: men more so than women have their identity very much connected to their work life and the transition to retirement is bumpier from what I've seen (I live in Florida, land of the retired).
It's also a bumpy transition for homemaker spouses who all of a sudden have their spouse around all day in their house. This doesn't describe how my spouse and I went into retirement but it's common for others.
You are doing the right thing by projecting and thinking what your retirement would be like. Most people are chomping at the bit for the freedom and I have loved every minute of it but not everyone adapts that quickly.
Golf, travel, gym, amateur photography, other sports like tennis, etc, these are all common interests. Volunteering is certainly commendable too if it fits your personality.
When you were a teenager what were your dreams? Now is the chance to accomplish them.
My spouse (male) belongs to computer special interest groups, photography groups, goes to the gym, we take one big trip a year with lots of planning in advance (half the fun is reading up), has a boat, goes to sunset meets at the beach (drum circle) to see friends, photographs wildlife locally and national park landscapes. It built gradually, not all in the first year, somethings got tried out and dropped.
One suggestion: dedicate a room in your house for your den or man-cave. A place that is all yours. Retirement is the first day of the rest of your life.