You will be surprised how complete the package from the Make A Wish foundation is. Your Genie pass acts as a fastpass, so you do not have to make them in advance. You will find cast members go out of their way to show Wish kids a great time. You will be issued buttons from GKTW so you are easily identified as a Wish family.
I would look on ebay for tradable pins, and also inexpensive autograph books. GKTW and Disney will also help you with your stroller issues. The passes provided by GKTW can also link all your photos, as the passes (before magicbands) did.
Knowing your situation, Disney dining (or your Make A Wish coordinator) will do whatever is possible to get you seating for the Crystal Palace, but the cost will be your responsibility out of the stipend they provide you with (Dollar amount is more then generous).
Is a first aid kit necessary? Other then regular meds, we needed nothing else.
I think you will be pleasantly surprised with the accommodations and perks from GKTW. They made sure we had a truly magical trip, from start to finish. Good luck!!!