We went last year and bought Mickey hats on Main St. We had Mom, Dad, and Nana printed on ours. When I asked, I said, "Oh I wish I could do nicknames." She said.."Mom, Dad and Nana aren't nick names" We had no problem..
Then somehow I lost our bag with the hats at the hotel (Swan) and we had them redone the next day.
We had no problem.