@BobKamman   I would simply follow the tax regulations as best I could, as there's always some give and take with clients (ie, the "same amount as last year" response).   These questions you raise are rhetoric? Though interesting, they have answers.  

You say "Be sure to tell them how much EIC they lose when tips are made nontaxable."
This comes close to suggesting the client should manipulate the information, a questionable approach.  Are tips in the course of business, taxable?  Is the tax preparer obligated to ask questions to ensure an accurate return? Yes.  So you ask the client what tips they received and they give whatever answer and you move on.