Playing devil's advocate here, as a parent this sounds great! Have your young children sit next to a couple strangers a few rows away: now you get some peace and quiet while other people have to deal with their seat-kicking, drink-spilling, whining, crying, bathroom trips, diaper changes, requests for entertainment, etc.

You know this is going to happen too: there are going to be some subset of parents that are not going to pay extra and will just choose to let the airline make their kids some complete stranger's problem. Hope the general public enjoys it.