What’s the polite way to word that you only want $ for the wishing well for ur wedding present?

I would like to know the polite way to word (not on the invite, on another card in the envelope) to say that you only want $$ or vouchers for a wedding present and that there will be a ‘wishing well’ at the reception that they should put it in.
Some out there may think I’m rude – (sophie wouldn’t have been invited anyway! – take the cake for rude!) I appreciate any advice RELATING to the question, not ur personal opinion. Remember what your mum always said, “If you dont have anything nice to say, dont say anyhting at all”.