No, your adult child should not say he is "exempt." He should complete a W-4 for his employers. If tax is withheld from his income, he can file a tax return at tax time to seek a refund. If you can claim him as a dependent then he is required to say on his own return that someone else can claim him.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
