Lucky you! But, it will be very hot, so Merrylegs is right, a villa with a pool is great to get away from the crowds. We tended to go to the parks early in the day, and came home at about 3 when we had all had enough, or had a chill out day at home, then you can always go out again later, back to the parks if you want for the firework displays. They are open later in the summer. We went in May and sometimes went to the parks at the end of the day when lots of people are leaving and the queues are less.
Villas are great, well equipped, but no welcome packs in the ones we went to (Virgin), not so good if you are arriving late at night, and you are all too tired to go to a supermarket, but starving and thirsty! Virgin are very good, if you need to phone them here, do it Sunday morning,so you don't have to wait in a telephone queue for hours.
We got a really good book, Brits Guide to Orlando, and the first time, got them to do us an itinerary, told them what we wanted to see and they organised it around the parks' less busy days. You don't have to stick to it of course, but it's full of really good tips, like making straight for the most popular ride immediately - no queues!
Outside the parks we really enjoyed the Kennedy Space centre, but don't think that would appeal to your 4 year old.
Swimming with the dolphins at Discovery Cove is fantastic but pricey, we did it as a one-off, and its beautiful and not crowded. Sea World is our very favourite place - do the Shamu show late in the day. Agree again with Merrylegs about Islands of Adventure, loads to see and do. Don't try and cram everything in, you just can't see it all and everyone gets 'parked out'and overtired.
Foodwise, we liked Bob Evans diners - nice big salads if you want them!
Ooh, also, if you live near Gatwick and fly Virgin, you can do twilight check in the night before and just walk through without the queuing in the morning, it's brilliant!
Sorry if I've gone on.....and on, have a great time!