It’s been about 3 years since our last visit to Mexico, so some of my information may be out of date.
The hotel that we’ve stayed in for 2 of our last 3 visits is the Flamingo Cancun. It has the advantage of having an all-inclusive plan, is centrally located on the beach, and wasn’t too terribly expensive. Is it the same as the 5 star resort we stayed out for the one trip? No, but it was clean, the staff was friendly, and the food was decent. They have 2 pool locations, so pleanty of room to sit by the pool, or on the beach. There are several second floor rooms that would be perfect for wheelchair accesability. I’d just call when you make the reservation and tell them you have a wheelchair and ask for a second floor room. Keep in mind that the first floor is actually lower than the second floor…so from the lobby you’d go down to the first floor. There are several bars, one by the pool, and another that is down by the beach. So if your friend doesn’t want to lay out or anything he can just sit, drink, and watch the beautiful scenery.
As for Chichen Itza I’m torn. How easy is it for him to get around? It’s not wheelchair friendly at all…and it’s spread out all over the place. It can be quite a haul from one end to the other. Were it me, I might suggest a trip to Tulum and Coba. Tulum is small, and you can’t climb on any of the buildings anyway…so your friend can get around to stuff a lot easier, and won’t feel left out that he can’t go up any structures. Coba does have two large pyramids that you can climb, and normally I wouldn’t perhaps recommend it but for one thing. They have guys at the entrance to the ruins that will peddle you in a little rickshaw sort of thing to the main sites. So that way noboby has to push the wheelchair. You can ride to the main buildings (there are only like 4 or 5 to see) and look from the comfort of the seat. Plus both sites are a much shorter drive from Cancun itself.
Don’t underestimate the heat. It’s going to be hot as hell in December…although you shouldn’t get the party crowd. Wear sun screen and drink lots of water…bottled of course.
If you could let me know any other types of things you like to do, I might be able to make some more recommendations. There are a ton of activities in the area, as well as sites that are a day-trip away. I’d be happy to ramble on much more if you’d like.