Below is from the Run Disney event site for the WDW Marathon weekend, but probably applies to all:
gEAR Bag Check is available for the Marathon, Half Marathon, 10K and 5K.
A clear plastic bag will be issued to you at Packet Pick-Up to be used for gEAR Bag Check service. No other bag will be accepted.
A numbered bag check sticker will be given to you at Packet Pick-Up. Place the sticker in the clearly defined area on your clear plastic bag prior to arriving at gEAR Bag Check.
At race completion, your race number will be used to verify your bag when you pick it up.
Valuable items should not be checked.
The Event Staff is not responsible for any lost, damaged, or stolen items.
As far as pics, I think marathonfoto is the company. After the race you will receive an email with a link to access all your pictures that were taken along the route. Now, Disney world pics are actually done through them and are completely separate. Even at the character stops other runners or cast members can take pictures with your phone or camera. Runners are a great group.
Enjoy. The whole family is going to love it!!!