Thank you for mentioning the Epi-Pen. I will add that to my list. DD is allergic to bees and I would hate to be without in case she got stung.We bring the epi-pen, camera, autograph books and pens, cell phones, tickets and whatever you are using for $, a small sunscreen and a lg. zip lock bag to put stuff in on the water rides or if we are caught in a down pour. With kids that age I don't feel the need to bring anything else. They do not need changes of clothes and if you need something else you can get it there. For example, DS9 got a rash on his legs from his wet shorts (mild allergic reaction) and we were able to get cream at first aid. We put it in one bag and took turns carrying it as we felt that was easiest.
If rain is part of the forecast, you may want ponchos as well. We only brought them when absolutely necessary as the are quite cumbersome.

I take DH and DS.![]()
Other than those two, we take as little as possible:
Camera w/ extra batteries and memory card - in DH's pocket
Each person carries an emergency poncho in their pocket
I carry all the park passes, room keys, etc in a holder on a lanyard (Walmart)
Our itineries are printed onto 3 X 5 cards, laminated and attached to belt loop w/ a caribiner
Sunscreen stick - fits in pocket
We don't carry water bottles. We get free cups of ice water.
I also take just a few (6-8) single serve lemonades so the tap water isn't so gross! Saves time and cash!