To make sure you didn't miss anyone, you could try doing what I do. When you start the "search" for the new chief, pause the game (spacebar) and drag each villager to the robe. (Nursing Moms and their babies won't try on the robe) Double check while the game is still paused that you have everyone. Unpause and see if you have a new chief. If you still don't, pay attention to your nursing mothers, and when their babies are two, drag the mothers and the kids to the robe. You should get your chief then.
in other words have a dog pile for the trying on of the robes? that is a very good idea and a funny one too.

with that many people that is a better idea than mine, start with the youngest kid and work up to the oldest 1 at a time, but i like your idea.