Ok, I'm going to be the lone dissenting voice. We love June because it is warm. We love the water parks and we love that the parks are usually open longer. That way we can go back to the resort (swim or relax) and still have plenty of time to hit another park when it's a little cooler.
OP, definitely spring for the park hopper option. If you're on a budget do the values, if you can spring for a deluxe go with BC. Your 10 yo will love stromalong bay.