My mother loves breakfast and brunch. Loves them. She and my father don't often go alone, because brunch is often a fun, festive thing for us. The greater number of her kids who can be there, the better.
So am I a part of the herd for taking my mom to brunch on Mother's Day? I don't think so. It's what she wants, and the day is about her.
As for the lines and the screaming children, that's what advanced planning is for. Pick somewhere that takes reservations. Make reservations for a time other than 11am. Go somewhere at least moderately off the beaten path.
The important point to realize, which Kass seems to miss, is that one mother's Mother's Day is another mother's hell. My mother likes late brunch and a stroll around whatever neighborhood the restaurant is in. This year was Francesca's Forno (can't recommend it highly enough for brunch, but haven't been for dinner) and a walk through both Wicker Park and Bucktown. Talked to Dad late last night: Mom's still gushing about her special day.