We have been to Antigua on numerous cruises and have done many of the excursions that have been mentioned:
Adventure Antigua Eco-Tour, Lawrence of Antigua Tours, taxis to various beaches, Excellence Catamaran and others. The Eco-Tour was our favorite but now we enjoy just taking a taxi to Valley Church Beach and putting our towels under the trees. Drinks and food are available at the Nest Bar. The water is an amazing color of blue but is not clear for snorkeling. There is a bit of a drop off down to the water but that should not be any problem for your family. It is now one of our favorite beach days and we will be back again in April.