Also, I got a Disney Visa credit card solely for the meet/greet inside Innoventions (the side of Innoventions near Soarin, not Test Track). Air conditioned line, with other stuff for uninterested family members to do while you and character loving people can wait in line. (There are video games right next to the Visa line my other DS does while he waits for us.)
You will meet 2 of the fab 5 together at once. They rotate every 20 or 30 minutes (a photographer told me once but I can't remember), and its either Mickey/Pluto or Minnie/Goofy. You get 1 free 5x7 photo (hard print out) on your way out at the photo shop to the left of the big golf ball, and can even personalize it with borders, signatures of the characters, etc.
If you go right at 1pm it can be a long wait. They will check for your Visa card before they let you in line, and give you a paper voucher for the free print. And, they won't tell you who the characters are (and hassle you if you try to ask someone leaving - fair enough, as they could change before you get to the front of the line). They only do this m/g 1pm to 7pm. (of course, characters and timing can change anytime, so check before you go).
DS is always confused when we go to the Visa m/g right after character spot - he wonders how the 2 changed clothes and got there so quickly.
Tip: Don't leave the Visa m/g for the last minute - on your wait out of Epcot. Your photo is not available immediately (for the free print out). They say 30 minutes but I've gotten it faster than that. Sometimes you can convince the photo shop person to give you another photo free, but they are supposed to only give you a print of the Visa m/g session (and only 1 print is free).
HTH!