Met Tiana and Naveen last Feb. It was their last set of that day, 5pm-ish, and that was my goal of the day as I had worn my Tiana shirt so I got there a little early (no more than 15 minutes) and was 2nd in line. Totally worth taking the extra time to meet them both, Naveen was amazing!
Pick up the times guide as you walk under the train station into MK and plan accordingly. Circle it, highlight it, set a reminder in your phone, whatever you need to make sure you get there if this is your little one's must do. And if you don't know where the location is, have a CM get you there earlier in the day. I missed her earlier cause I couldn't find it.