General tips for saving battery on any smartphone:
1. Turn down the screen brightness as much as possible (biggest and easiest thing you can do). Of course, darker screens are harder to see in bright sunlight, but you could always just find shade or go inside somewhere.
2. Make the screen-off timer shorter and/or don't turn on and off the screen as often. Touchscreens consume the most battery power on any smartphone, so turning them off for longer periods of time will conserve more and make sure your phone makes it through a longer day.
3. Kill apps that request a lot of data, e.g. Facebook/Twitter/email updates, auto-refreshing weather apps/widgets, contacts/calendar syncing, etc. If you have these apps, go into their settings and switch to updating manually, otherwise they'll continue to update at set time periods, and that uses up battery. Think of it this way: if you're not even looking at the app, why let it send you more data? It'll update when you open it anyway.
4. Turn off Wifi and bluetooth while in the parks. This effect is usually very minuscule if it helps at all, but every tiny bit can help. You're not using it anyway (well, most people don't). Same deal for GPS, but many apps like Mousewait utilize it so I usually leave it on.
5. As someone said before, use it only for communication. Being bored in line or waiting for a show, it can be tempting to play a game or watch a video on it while waiting, and I'm as guilty as the next person

. But you're in
Disneyland! Soak up the ambiance and atmosphere instead, look around! There's plenty of cool details everywhere to entertain you at least for a little bit
EDIT: P.S. If you have a digital camera lying around, use that instead of your phone! Even old point-and-shoots often take better pictures than any smartphone's camera, and they have longer battery life too.