It’s a bit lopsided… I’d personally reach out to the 13 year old first and make sure he understands what he’s doing. If he has any kind of real explanation for why he’s making the trade… let it pass.
Say for example he said “I’m worried about Barkley not seeing as many short passes now that Eli isn’t playing anymore and I think the Steelers are going to be down a lot and forced to throw and get Juju the ball a ton”. But if you ask him why he is doing that trade and he can’t really explain why, then I’d probably veto it.
The only reason I wouldn’t out right veto it is because it also kind of undermines the kid a bit. I get the idea of trying to publicly shame the adult but I feel like at 13 you don’t want to just go making decisions for him. It’s very possible he has some kind of reasoning for why he’s taking the trade and in that case I think it’s fine. As others have said, it’ll likely blow up his team and it will be a learning experience for him in future years.