Take note of the Baby Care Centers. They have changing tables, feeding rooms (with rocking chairs) high chairs etc in addition to supplies for purchase. They're all air conditioned, which can be nice during the hotter parts of the day.
Definitely pack clothes in layers.
I second the lightweight stroller. We love our Baby Jogger City Mini for Disney.
Stick to their routine as much as possible, but be flexible. My kids like to fall asleep on the bus on the way back to the hotel, and the transfer can be kind of rough. It probably would have been better to just have nap time in the stroller more, but DH likes his breaks.
Read up on Rider Swap, so all the adults can ride everything with as little wait as possible.
We actually didn't change our touring much when DS was a baby, but we go pretty frequently, so skipping stuff isn't a big deal. He was always awake super early anyway, so Rope Drop was easy. Then we used FP or Single Rider lines, so I've never actually done Rider Swap.