It's a bit complicated, as it might require some more time that it should for e-mails from unknown senders to get to your child. Anyhow, most legitimate people will probably reply, so your solution is probably going to work.

The only thing is that sometimes, by replying to spammers, you let them know that you use that address, so it becomes more valuable (and used) by them, that is to say your spam amount may grow. But, then, it's a minor problem: it always grows anyway. :-(

Michele.