Latrice, welcome aboard! The Dream is a great ship for your very first Disney cruise! That is the very first Disney ship on which my family sailed as well. You will certainly enjoy every moment!
When you board the ship, stop by
Shutters, the onboard photography shop. There, you can chat with one of the Cast Members to schedule a private photo shoot on Castaway Cay. Quite often, they do that for wedding parties and other celebrations, so I'm sure they'd be happy to accommodate your family as well. They can give you the details about pricing and extras when you stop by Shutters. I do believe that Mickey and other characters can be available for private photo sessions such as this, though there is a significant price increase to include the characters.
Have fun as you continue to plan your late summer sailing on the Dream, Latrice! Please stop back here and let me know how else I can help!