Baby Shower.

Due to a certain medication that I have to take I'm unable to breastfeed, therefore we formula feed. Just the other day, I was thinking about my baby shower and how I wanted to have a diaper raffle. Then I got to thinking maybe I could do a formula raffle? same jist as a diaper raffle but with formula. of course I don't expect anyone to buy anything, however if they wanted to, I would add a little card with info about the raffle and the type of formula we plan on using. Is this a bad idea? do you think it's rude?