iTunes / IT experts

My son piggy backed off my wife's iTune account for years

Now he has come of age and has his own credit card he/we want to get him off my wife's account
But it won't let us start a new ID with his email address.

Any ideas I can pass onto him ?

Let him open his own account with his email, then let him be bombarded with the 300,000 apple emails a week. Part of growing up.