We have gone many times to this photo opportunity. As said in other posts, they do not keep track of your card # or anything. Don't forget, it is 1 photo per card not account. So if you and your spouse have a card then you are entitled to 2 vouchers. They also do not care if you use it exactly on the picture being taken. There have been times when the picture did not turn out that well and they were happy to give us a different 5x7 that was taken that day in the park. Also, we saved our certificates that were not used and have used them on another day.
Yes, you can go each day of your trip. the only characters ever there are either Mickey and Goofy or Chip and Dale. You will be ale to meet either one of these pairs. I think they do it that because then not as many people will return numerous times to keep taking pictures of the same characters.
Most of the times we have gone no one else has been there so my daughter has had a lot of fun with the characters.
This promotion is supposed to run through Sept 06!!! (along with the free strollers)