Address book, stamps and pre-addressed labels (there are mail boxes at Disneyland, but they will be postmarked from Anaheim, not Disneyland, also there are no Disneyland stamps)
Autograph book and fat pen (easier for characters to hold)
Back pack
Bandana - can use to keep sun off neck or wet down and wear as a cool wrap on your neck
Camera and batteries, video camera (disposable camera -great for the kids)
Cash, credit cards, traveler's checks
Clip on case (most handy) or pocket case to put glasses in during rides (so they don't get damaged or scratched)
Disney guidebooks and notes
Drivers licence
Emergency numbers or contacts from home
Fanny packs
Garbage bags to use to bring clothes to the laundry room
Ground cloth to sit on for parade/fireworks (I love the Neat Sheet - takes up much less space than blanket or pillow)
Gum
Hat
Health Insurance card
Insect Repellent
Kleenex -purse pack size
Lanyards with secure plastic pocket for Park Hopper tickets and Fast Pass. (To keep them safe, handy and dry)
Laundry bag, soap & dryer sheets -pre-measured and in ziploc bags
Lip balm with sunscreen
Medicine (Prescription and over the counter)
"Mister" fan -battery operated fan with spray (during hotter months)
Moleskin and other "foot fixers"
Park Hopper Passes
Pennies & quarters for the penny press machines
Plane tickets
Playing cards/travel games
Proof of auto insurance-for car rental
Rain ponchos/umbrella
Safety pins
Sensible/comfortable walking shoes
Sunglasses
Sunscreen (Aloe Vera for sunburn)
Sun Visor
Sweatshirt or Jacket for cooler California mornings & evenings
Suitcase (empty to bring back all those souvenirs!)
Water bottles
Wet wipes
Ziploc bags