Are there a lot of mosquitoes or insects in Hainan?

My son is easily scared by flying stuff but he also likes tropical places with beaches (so that he can build sandcastles) and palm trees (he likes to climb them). Please also advice on clothing. What colours should we wear? Long sleeves or short sleeves? Do we have to bring sunscreen? I would also like to enquire whether we can have a Tiki themed house or bamboo house beside the seashore. It just makes a holidy much more enhancing and memorable (: