Hi Lori,
We just returned from Walt Disney World where I had
pre-ordered the Disney's Photopass Photocd prior to our arrival. Once there, we just had pictures taken whenever we saw the "khaki vest." And don't worry about having more than one group; all the Photopass cards can be combined once you return home to actually order the photocd. Also at this time, you will be able to upload your own photos. Once all the cards are combined and your own photos uploaded, you can order the photocd that you already paid for.
I did include a link above that takes you to the pre visit page to order the photocd, if you'd like to do so.
I love having pictures of our entire family! Otherwise it seems like there is always the missing person who actually takes the pictures. And by the way, the Disney cast members will be happy to use your own camera or phone camera, too.
Please let us know if you have any more questions; we are happy to help!