Our parish has a St. Nicholas event for this type of situation. A man in our parish dresses up as St. Nicholas and gives the children gifts from their godparents. So just separate St. Nicholas day from Christmas first. Then work on teaching the reality later.
My kids are the spoil sports, we have never believed in, or attempted to get our kids to believe in Santa. I was never taught to believe in Santa, so I had no inclination to have our kids do so. When you grow up poor, you figure out that all that Santa stuff has to be fake pretty quick
Our kids go to the event, they know the gifts are from us or their godparents, but they aren't allowed to shatter the illusions of other people.