the Riu resorts a probably some of the best for family's. We just booked our trip with them and they have some good promo's going on. Tak a look at
www.bookit.com. You'll find great deals for sure. Also, go all inclusive - it really is the only way.
(as for the Palace Resort comment earlier. I got married at the Moon Palace in Mayan Riviera - by far the best resort I've been to. It can be pricey but if you can get a deal - TAKE IT!)