I don't think its rude either, friends of ours did a wishing well, but people could also buy a gift if they wanted to. I'm sure there will be plenty of people who give presents still, its probably a recommendation not a necessity. Do whatever you feel comfortable with Thats the most important thing, they aren't going to care either way. It just makes it easier for people when they probably have everything they need anyway. There will probably something similar to a wishing well setup so you can place cards/envelopes there.