Great Thread, Great Input. . .
+1 on getting an Airhead to play with -- both for riding and wrenching.
Small/medium size bike idea: Excellent, and you might find that wrestling it around the garage, etc., is a LOT easier than that RT. I've found that, as I age, one of the hardest things is just moving the bike(s) around the garage. No matter how hard we try, our "core" strength is going to diminish, thus reducing our ability to handle larger, heavier bikes, even w/o a short inseam. Perhaps a subtle thing, but no less real for that.
Retirement, a/k/a "[I]Entire[/I]-ment" -- I've been "at" this for almost 12 years now, and it is something SO vastly different from a working life as to be impossible to describe to a working person. Trust me on this -- entirely different, and it may take a couple of years before the wonderment fully sinks in. As others have suggested, give it some time before making precipitous decisions (like selling your baby) -- you're in a very different space now versus the working life, and new interests and activities will ebb and flow according to the rules of the universe; impossible to predict.
It's the [I]What Is, As Is.