Spending so much time taking photos and using the My Disney Experience App can drain your phone battery pretty quickly. You might want to consider investing in a FuelRod.
Any type of external battery pack is good to have when you are spending all day in the parks, but it's particularly useful to get a FuelRod.
These are on sale in the parks for $30 and what makes them so good is that if they run out of power whilst you are using it, you can swap them for a fully charged one. This means you never run out of power in the parks.
FuelRods are the size and shape of a large lipstick so don't take up much room in a pocket or bag. They won't fully charge your phone from 0% but you should get enough to keep you going. Also if it runs out and you need more charge, then just swap out the FuelRod for a fresh one.
There are more powerful portable chargers available elsewhere but if you're spending a long vacation at Disney or are planning on going more than once, FuelRods can be an excellent investment.
Even though you can pick these up at Walt Disney World, you can get them elsewhere in the US for slightly cheaper, including at Orlando International Airport.