Just wanted to echo what others urged -- try to plan for a later Finding Nemo show. While we've made it in and out in 60 minutes before if we were seated immediately and the characters came in quick succession (e.g., lunch at Akershus), character meals can easily take 2 solid hours, especially if you end up having to wait to be seated. Our longest-ever character meal, an early dinner at Crystal Palace, clocked in at a whopping 2 hours and 40 minutes, which included a 30-minute wait just to be seated: and to add insult to injury, when we finally gave up and left more than 2 hours after that, two of the characters still hadn't reached our table yet!
Even if you don't end up needing that extra hour, you'll be able to relax and enjoy your meal more knowing you've got that time cushion. If you end up finishing early, you could check out the earlier Finding Nemo show and see if the available standby seating meets with your approval.