The good news for you is the schools in Texas have Spring Break start in March!
Harvest Caye is actually quite nice, especially if you are able to walk around on your own!
Many people complain about how far it is from the ship, however, it is not really any further than at most ports. The other complaint is that food and beverages are NOT included.
If you get hot, look for the misting stations, and there are shaded area to enjoy.
The pool is large and clean. One of the excursions we enjoyed was the Electric boat -- short, but was fun and enjoyable tour off the island. Also, don't miss the carvings, and animals/birds.
(There are carts to ride, to and from the ship, if needed).