We've used Kids Clubs which all 3 three of my boys LOVE! They've been to ones in Mexico, Aruba, Dominican Republic and Florida, all of them have been excellent. There's usually a bunch of kids in the club during the day with 2-4 instructors. They'll take them swimming, play games, built sand castles, feed them lunch, dance, have races, arts and crafts etc. There's something there for every child from ages 3 to around 11ish and they do activities that i wouldn't be able to do with all of them. My boys always make new friends and have a blast. We drop them off at the kids club around 9ish and pick them up around 3ish so we can spend time with them (dispite the three of them begging to stay). It gives my husband and i some time to ourselves and its very safe. The instructors have experience with children, CPR & First Aid certifed and will answer all your questions. At some resorts they're willing to help you out after hours.
I've also seen hotels that have babysitters that come to you. I used them once during the day (didn't like it) and once at night (was good.) She came to our room, brought a board game and a disney movie and watched our boys for about 2 hours. She was very good and once again experienced with children and first aid/CPR certified.
If you find a kids club, i'd look into that. Best wishes to you and good luck! =]
mother of 3 w/ 1 on the way, <3 kids clubs