We've been a couple of times with toddlers - our son was 4 the last time we went - and know from experience how tiring the days can be on little legs. So I'd maybe think about going back to the hotel room for a couple of hours each day to recharge, especially seeing as the park's probably going to be open late.
One thing I would decide in advance is what day do you want to watch Dreams on - there's no way that DS would stay up until 10 to watch it unless we went back to the hotel for a little while. Personally I'd think about getting a late start on that day, maybe going back to the hotel for a couple of hours in the afternoon, having an early tea there and then heading back into the park for the parade, rides and staking out our spot for Dreams.
If there's more than one adult going then you could try one of you heading back to the hotel early with your little one while the other takes advantage of the late night opening and stays in the park and then swapping the next night. It's not as much fun wandering around on your own but you'd get more time for the adult rides! There's also the baby swap service.