The cool thing with Gmail is that you can add a "+son'sname" after your real email address, and it'll just get sent to your inbox. The problem will be if this system accepts that or not. Some systems don't.
So for example, your son's name is Bobby. With Gmail (only), you can make up and email address for him:
Then you make a label called "bobby" in Gmail, and when email comes in for him, it'll be labeled "bobby".
Hope that's not too confusing. It helps when you sign up for stuff you don't want to get. Like email@example.com. I put that in for the stuff I have to put an email address for, and have a filter that says to delete everything with a +junk on the end of my name :)