Alzey is a historic horse trading center from the middle ages, and not a bad place to spend a day. The Schloss, which is still lived in and not open to the public, is really something.
But I suggest Bad Kreuznach would be a better place to spend a night. It's also historic, has a good Roman museum, and the ruins of the old castle have a good gasthaus. Plus there's the caves used as air raid shelters in WWII. It does get a number of tourists, but rarely Americans.
Even better would be Meisenheim, where the old city wall still stands and which is much more attractive than Alzey. It's less than an hour from Ramstein. Meisenheim is known as a place where Germans go for romantic weekends. The Meisenheimer Hof is excellent, both for lodging and food, it's Michelin starred, and not inexpensive. There are a couple beer gardens that are much more reasonable.
In mid-September Bad Durkheim will host the worlds largest winefest. It's not "on the way" but it also is only an hour from the base. There will be numerous other winefests within the Pfalz, hundreds, and some are quite small. I have a link somewhere, I'll look when I get a chance.
If you want to travel down the Winestrasse I'll recommend either Freinsheim or Deidesheim, both medieval walled towns that are excellent places to visit and very off the beaten path. Deidesheim is more expensive; it's basically a German version of what Callistoga was to Napa Valley 40 years ago.
Note you will need a visitors pass to access the base, and your son will need to be there with you to sign you in. You need to do this at the West Gate, on the right as you approach the gate. You will need vehicle papers and passport also.
