Okay, in the future, I will take your collective advice and approach the parent. I guess I have seen/heard so many times where the parent of an unruly/misbehaving child(and I really want to stress that I didn't know/think she was handicapped until the manager said so!) gets bent out of shape when you ask them to kindly restrain their child from throwing blocks at the other children, or screeching obscenities in the restaurant(true stories, I swear), that I usually skip that step in favor of having someone who has "authority" (albeit a meager sort) step in.
Like I said, I'll take your collective advice under consideration for sure, but that's where I was coming from when I approached the manager.