The most popular things to do in Belize are going to be either the cave tubing, which your children are too young for (there are age requirements) or snorkeling which is supposed to be excellent. If your kids do not snorkel, you can take a trip to one of the Cayes (pronounces Keyes) and hang out on the beautiful beach or there are things to do on mainland of Belize. I am taking a tour to Altun Ha mayan ruins & then to the Belize Zoo. Look at old posts for info on Belize Zoo. In Roatan, this is another place that is big on snorkeling/scuba. We are not going to be there but for 6 hours so we are taking a cab to West Bay beach area & just having a beach day. You can snorkel right off of the beach areas there.