We started out saying NO GIFTS PLEASE, way back at the baby shower. I'd rather say that than lay out the parameters of what's okay in our house. When people insisted, we said we were saving up for a bike carrier and would love help with that.
Later, when people insisted (and many did), it usually came along with the question, "What would you like for the baby/kids?"
We'd tell them that we like books, art supplies, experiences, and contributions to their educational...