Our first time there we MISSED Mickey and a few of the other characters. I don't know what happened, but they miss-timed seating us, and they totally missed us. We had to go stand at other peoples tables (brought over by the wait staff) to see them. It wasn't comfortable for us, or the peoples whos tables we were standing at....
We went the next year for dinner, and all was fine. There were about... 15 of us, and were were there over 2 hours, but we had great interaction with the characters this time. We were one of the last families in the restaurant (late ADRs + big party), and I guess they were a little bored, so they really hung around with us.