Tierras del Sol is a fantastic place, the very last "hotel" (really just a handful of rooms and a palapa) on the road before you enter the Sian Ka'an nature reserve, but they are tiny and when I checked their prices have gone WAY up since we were there.
Ana y Jose's is probably where most wedding parties head to, but they too are expensive. Really, all the hotels along the strip south from the ruins are fantastic. We saw weddings there.
Oh, wait, you said "all-inclusive". Ergh. I'm not a fan of all-inclusives, because there is so much more to Mexico than steam-table buffets. But I guess if you're going to the Tulum area it doesn't matter TOO much, since the restaurant options along the beach road are somewhat limited.
Do make an effort to get out of the bubble, though -- the puebla or town of Tulum, up on the highway (just past the turnoff to the beach road) is an interesting place to walk around. I STRONGLY recommend taking at least one organized tour, at the very minimum a visit to a couple of cenotes (freshwater swimming holes opened up when the thin limestone crust of the Yucatan caved in). We also did an amazing walk and float through the three lagoons in Sian Ka'an, arranged out of the Weary Traveler hostel in the puebla. Your hotel should also be able to set you up with something.
As I've never stayed at them, I can't recommend one, but when we went I found the forums at playa.info and tulum.info to be extremely helpful. They're the same people; playa.info is for Playa del Carmen, but gets the bulk of the Tulum discussion as well. They have a whole section for All-inclusives. Do a search for "wedding" and dig around a little. Most of the people who post there heavily are American ex-pats or frequent visitors who really know their stuff.
If you're really bored, you can read my entire "Trip Report" that I posted back in 2005, before I knew anything about anything. I don't actually get to Tulum until Page Three. There's not a lot in there that speaks to your needs, but you might laugh.
http://www.playa.info/playa-del-carmen-forum/12969-where-i-went-holiday-trip-report.html