Is their dad deployed? You seem to have your hands full and I hope everything goes well. I would absolutely call and double check about what rides your kids will be able to ride without an adult. Honestly sending a toddler on Dumbo seems very dangerous. I know they are secured somewhat, but if a small one decided to hop up things could get ugly very easily!
You
7.5 yo
5 yo
5yo
15mo
newborn
How are you dividing them up for rides?
Moneywise just with what you posted you have $1490 or so left over to play with. That may or may not be enough. What you might do is decide how much $$$ each kid gets for souvenirs (and include yourself).
So if you say $75 for the 5 of you to get souvenirs that would be be about $375, knocking you down to about $1,100 for the rest of all the incidentals.
For our family of four we pay for the dining plan, the hotel, and tix in advance. And then we pay for souvenirs and tips OOP. I think on those extras we usually spend about $1,000 for a week stay.
I hope it works out for you!