How many people would you expect to be on a dive boat in June or July? We are looking for smaller numbers because we are diving with children.

I think that will depend on whose boat you're on, and how busy they are at that time. In August I was on the BonBini afternoon boat several times, and there were from 8 to 11 passengers. Do you know where you'll be staying? If they have a dive operation they can probably give you some info based on previous years.