One reason you might want to steer clear of Mata Chica is that it is pretty far north of the river cut, in my opinon. That means you will need a boat ride back and forth - boats don't run in stormy weather, nor at all hours, so you would be limited by these factors. Search this board for North & River and you will find the pros & cons. What do you mean by hang out? Hang out alone in your hammock, under a palm tree - then mata chica could be perfect. Hang out along the beach, with diffent people & entertainment, at various fine refreshment stops - then you will probably not like the isolation up north (hammocks & palm trees can be found anywhere).
There are many trips to fish & snorkle on the way to & fro Caye Caulker, we go at least once per trip for the past 13 years, definitely worth it -IMHO.
In April I have experienced Warm Sunny Tropical weather with occasional storms and wind shifts. 83-93 degrees F, variable wind, water temp in the 80's. Perfect IMHO!