B.D.
Hi! Just got back from PR on Saturday...stayed at the Conquistidor. This is a beautiful resort with a private beach. Depending on when you go (from what I understand) they do have activities for children, but you will need to check with the hotel. Drawbacks: food is expensive, activities associated with the hotel are expensive, 1 hr commute from the airport (thus, removed from other site-seeing activities). Benefits: beautiful resort, private beach/island with oodles of amenities (no one hassling you on the beach to buy things), water park, shopping, harbour, etc. If you truly want to get away and stay ay one location, this is the place to be.
Hope you have a terrific vacation!