The first year we went, my daughter skinned her knee and they were out of band-aids (lol), so we always bring some.
Bring some cash if you need to tip shuttle drivers, etc. They don't have an atm on-site.
I always stop by our local store and pack some individual apple danishes, cinnamon rolls and those bags of cereal. That way, we save a little money on breakfast, can relax longer in the room, and have extra space in our luggage for souvenirs.
They have some great deals for pizza delivery to the Hojo, and the front desk can give you the menus and explain the specials.
They do have a printer and computers you can use to print out your return trip tickets in the lobby. There can be a bit of a wait sometimes, so don't take too long to get that done.
There is a laundry room in both buildings 1 and 2.
Lifeguard at the play area goes on break occasionally, so along with close time, check their break hours so the kids don't have to wait to slide.
You can buy ART passes for the little shuttle to and from DL. We usually do, just in case we have a bunch of packages or a very tired kid. They can also set you up for local trips, etc.at the front desk.