I guess the big question for me is, when do you normally do meals? My kids are used to a big(ish) lunch about 11-11:30 in the morning, and a smaller supper around 5. So, when at Disney, I tried to stick to that timing. So, if it were me, I'd do the 5 supper, because if I tried to wait until 1:40 for lunch, the kids would either be starving or have eaten enough snacks to not want to eat anything. Since most of the BBB girls I've seen have their hair still looking great hours later, it wouldn't seem to matter about it being a longer period of time after.
ETA: Since you're doing Epcot that day, you can spend part of that waiting time wandering around the world showcase & meeting the princesses there, too, so you can still get gorgeous shots of her with princesses before the meal! Or after if you go with the lunch option.
-Kris
DS (9/05)
DD (8/08)
DD (9/12)