There are several newer, large AI resorts down the coast from Playa del Carmen to Tulum. The resorts themselves offer more amenities and activities then hotels on Cozumel. There's also the added benefit of lots of interesting off-site diversions - Xel Ha, Tulum, Coba, Aktun Chen dry caves, great snorkeling, cenotes (diving and snorkel tours) and several very nice beaches, also more touristy shopping and restaurants and bars if you want them in PDC. All depends on the ages of the 15 kids and interests of the adults. If you're at an AI it doesn't really matter where it is because you're going for the resort, but, if your groups wants to take in a bit of Mayan culture or see a less developed (compared to Cancun, Cozumel) area of the Roo, it could be a good option.
The ocean diving around Akumal is pretty nice. No walls or really deep dives, but the reefs are very healthy. I have no personal experience with the AI's. We rent a condo on the beach in Akumal every year the week before Xmas (low season prices and no crowds at all). At least 3 turtles every dive. Every type of angel fish in abundance (schools of 8-10 gray angels), lots of eels, rays, grouper, baracuda and all the usual tropicals too. And, some of the largest elk horn coral I've seen anywhere. Dives are usually at 9, 11 and 2p. Easy drift dives with depths 50-70, and we avg 50-60 min dives. Sites are at most 10 min boat rides. Eagle rays come right up into the bay just a couple feet from the beach. So do large turtles. At night in Half Moon Bay you can snorkel and see tons of stuff. You could also take the ferry over to Coz a couple days if you wanted to for diving or just a day trip.
When we first started going to the Riviera Maya, I found
www.locogringo.com to be very helpful. Lots of general info on the area as well as extensive listings, descriptions, photos, reviews on AI's, hotels, condos and villas from PDC and south down to Mahahual (sp?)
