I think the walk through customs has gotten shorter, but the airport has been prone to construction detours. I would suggest asking one of the flight attendants on the plane (they're likely familiar with the airport and gates) and perhaps arrange a wheelchair or other transportation if it seems as if it's going to be a problem. I know that when I had a fractured ankle during the summer, being immobile (as on an airplane) for long-ish periods of time and then emerging into a hot/humid environment was particularly difficult, much more so than once you're a bit more acclimated to the temperature.
As far as the beach drinks go, I do believe they have flag service now, but even if this proves to be rather sporadic for some people, I really cannot imagine you would have any problem being accomodated by the staff or even other guests (I for one would be more than happy to run to the bar for somebody in your situation).
As far as non-draft beer, I don't know, since I don't really drink beer, but I do believe I recall seeing bottles of beer in my husband's hands at varous points.
As you may be aware, CSS is built up a hill, and there are numerous steps. However, there is an available shuttle to bring you from the upper part to the beach part, and they are very quick and accomodating. I can't really think offhand of anyplace on the property that isn't accessible with crutches, and if you choose to walk around and explore, there are ways to very much minimize the number of steps (i.e., taking the back service road or the winding pathways).
You definitely have my sympathy, as I remember how irritating it was for me when I had my ankle problem (many moon ago), but I really can't think of a better place to recover!
Customs lines move quickly, just make sure you fill out 2 immigration forms not one. We were told on the plane by the flight attendant that we need only one form if we are husband and wife; however, when we got to the customs officer, he told us to step aside and fill out one more. Not a big deal but by the time we filled it out our entire airplane was ahead of us in the line.
I had bottled Heineken at CSS.
As of September 2008 there was no flag service at the beach.
You might want to request a room that's close to one of the places where the shuttle-van stops so you can get around easier. You'll need to call them a few minutes in advance.
We were in Building F, right by the Lobby ( great views too ) and besides the flight of stairs to the room- it's as close as you can get to the Bellman stand and the shuttle-