If your kids are older, at least pre-teen, my vote would be for xpu-ha. You need to love nature, the beach, and Mexico. It is located about 1 hour south of cancun. My husband and I absolutely loved it (left toddler and pre-schooler home) and can not wait until the kids are old enough to take them back. It is truly paradise. Almost feels like animal kingdom!
We've been to sandals and xpu-ha has a much different feel.