Grooms Cake Question

I'm thinking of getting a grooms cake to surprise FH. The baker has hasked how many ppl I plan to feed with it. Any suggestions - is it supposed to be big enough for everyone to have a piece??

If you are having it at the wedding

No, they usually don't need to be as big or to serve as many people. Esp if you have a plated dessert. I still figure it's about a slice per person from one or the other so if your WC covers everyone, I don't think groom's cake needs to be over 25% . .. they are usually more for fun an flavor than feeding. .