The number of photo packages is based on the number of people in the party. According to Allears.net, it's one package for parties of four or less, two packages for parties of five to eight, etc. You take the photo with Cinderella downstairs, before you are seated and the package is delivered to your table during your meal.
Whichever Princesses are making the circuit that day will go to all tables and pose for pictures. The exact Princesses vary so there is no gaurentee who will be there. For example, when I went in December, the upstairs princesses were Princess Aurora (Sleeping Beauty), Snow White, Belle (blue dress), and Ariel. Others have reported seeing Jasmine and Mary Poppins.
Each boy will get a plastic sword and girl gets a wand. If you wanted, I'm sure the adults could get swords/wands if they wanted. I'm a adult and they gave me a wand.
The experience is a lot of fun. The food was okay, but we went more for the experience and chance to eat the in castle.