Each park has a baby station, an amazing place for moms and little ones to relax, change, feedings, bottle warmers, and get anything that was forgotten, super clean too. The baggies with outfits a must.
Also for the stroller, if it rains, use ponchos to cover the stroller, or other plastic covering when you go onto rides. Nothing worse then getting out of a ride or show and finding stroller all wet. Also put something ( ribbon, bow, luggage tag) on your stroller. CM may move the stroller around in stroller parking. Makes it easier to find yours. Oh, never leave anything in the stroller you don't want lost or walking away, even umbrella.

Take one bag with necessities, the diaper bag is great for holding that and camera, wallet etc... Going through security check with several bags is way too time consuming.
I also dressed DS in onesies that were like a little cute cotton shorts outfit onesie, Carters has them. They are easy on/off and easy to pack 2 or 3 in diaper bag.
Best thing was what somebody told me, don't stress, stick to baby's schedule not yours and things should go smoothly. Keep in mind that strollers have to be closed up on busses and most boats, so baby has to be out of it. Strollers can be left open with child inside on monorails.
Enjoy and special magic always happen for the little ones