If he trains under supervision I don't see the problem. Any sport has even greater risks. His Tae Kwon Do. My son had entered a meet under my supervision at the age of 9. He pulled 135 at a weight of 65. He did his first meet this year going 245/155/360 raw at 132 and the age of 16.
He has never suffered an injury other than some strained upper back muscles, maybe DOMS soreness related that I treated that day. He has however suffered a broken arm while wrestling and other injuries in team sports.
His sister has suffered stress fractures and shin splints while running in track and cross country. Both more serious injuries than when they have lifted. She's actually planning more lifting to strengthen her body overall to handle the rigors of running better this year.
I think it's mainly perception with the powerlifting. Also their dad, me is an ART trained chiropractor ands they have access to me in my office gym, so I don't let little strains etc. grow into big injuries.
Powerlifting is just lifting. Watch the kids close, limit maxes and keep that form tight. If you do that it's less likely for your kids to get hurt than playing your average team sport. and don't get me started on those two darling sports for the young ladies, gymnastic and ice skating.
The perception should be the other way around. Has anyone ever seen their injury rates?