We also did a wishing well for our wedding as we had moved two house into one unit together so not only did we have everything we needed we had two of them. One thing we didn't have was a good lounge suite so I said that is what we would be buying with it so people knew what we were going to do with it. With the invitation we provided the envelope so it would be completely anamolyous (sp?) and the wishing well was placed on the table at the entry to the reception next to the table seating list so it was visable to all guests.
Before our engagement party I was going to do presenets but after getting over 20, yes you read it right, 20 platters I opted for the wishing well.
I do not think it is rude to ask for a wishing well over presents and I am certainly not a shallow person!!