I also went to aventura spa palace which has aventura cove attached to it for kids and it was awesome. Great food, great service, and really friendly staff. It doesn't really have a beach though. The pools were great. There's also a fantastic spa.
One thing to remember is to be extra safe about the drinking water and anything that's washed in tap water wherever you go in that area. At Aventura Spa Palace, there were signs everywhere saying the water was safe. I took a tour of the kitchen and then sanitize the water with iodine before washing fruits and veggies in it. I'm not sure if that's safe during pregnancy?