It sounds like the suggestion was made after the item was given. I have a problem if there was pressure put on the recipient, but I don’t think a suggestion is so terrible, as long as the donation doesn’t go through the previous owner of the oven (because if it does, since he’ll know if the tzeddakah was given, that’s a form of pressure.
OTOH, in the case of gemachs, I have no problem, since the donation is requested in advance. They could rent or sell it privately if they want, so all the better if the money goes to tzeddakah).