The condotels and suites places (like Banyan Bay, Xanadu, Belizean Shores and similar) tend to attract more families, especially in the summer. You might look at "full service" resorts such as Victoria House, Portofino, Mata Chica and similar). None of the properties on the island is really huge -- the largest ones are under 80 rooms -- so herds of kids are not really a major factor at any of them.
--Lan Sluder