Is their a website like Yahoo Answers for younger kids that aren't old enough to be on Yahoo Answers?

Not really, no. I tried searching for one but I doubt it would have as good of feedback, either, you know? YahooAnswers does so well because of all the users on here.

I don't think it makes a difference. If he's just going to ask a homework or game related question or something I'd just let him use your account. If he's asking about using YahooAnswers, it doesn't sound like he's too young anyways. It shouldn't be a big deal. They just put an age limit on it because there is some adult content,which if they left unwarned they could get in trouble for by nitpicky parents who are shocked that there are bad things on the internet, but you can run into that anywhere on the web.

It wouldn't do any good. There's no way to enforce that kind of rule. On the internet, people can claim to be anything they're not - younger, older, male, female, and anything else.

Older people would get on that site and pretend to be kids - telling them anything and a lot of them would believe it. And that could get scary.