Well Zach, considering that it IS the end of school, expect some mild to high crowds, especially at WDW. You Probably would be able to cram all of these parks in. It would be a tight schedule, but still be able to have fun. If you are going in a few weeks, then no the Halloween stuff won't have an effect on your trip, but if you are going this fall, the parks would be a tad busier but nothing to notice. And some pointers, Pack some cool clothes, Florida is hot and muggy during this time of year. And also pack a poncho, this Is hurricane season you know! If you need any more help i would be glad to help!
The Halloween Stuff should be pretty cool. I heard The Mickey's Not SO Scary Halloween Party is cool, you should try to get tickets for that or halloween haunt at universal.
>> Jake