Well, I can see why he doesn't want them aged up, though. Still, it would be interesting to see a film with aged-up Parrs. bsky.app/profile/mrco...
Stefan EllisonBrad Bird has said the Incredibles' powers are meant to represent each specific member of a family (e.g. 10 year olds being hyper, mothers being pulled in multiple directions). So, knowing that, it makes sense why he doesn't age them.