I'd suggest, if you can't be there first thing in the morning, and slides are important to you, go later in the afternoon. By 2:00, a lot of people are exhausted from the running around in the hot sun and the swimming. This is even more true in Blizzard Beach because there's fewer shady spots, but really, in the hot humid summer months, the sun's gonna knock out anyone in either park. So by 2, lots of people are done for the day, going back to the room for a nap and shower before dinner. No guarantees, but it's often a good time to sneak in. Enjoy yourself right up to closing time.