When I was married to my son's father (may he rest in peace), we had three young boys in our home for Christmas...Bobby and Don's two sons from a previous marriage, Richard and Tommy. I chuckle remembering what we did to keep them believing in Santa. We would wait until they fell asleep and we would go around the house and jingle bells and Don would Ho, Ho, Ho outside their bedroom windows. Having them still believe made us feel younger! Each Christmas would also have it's own theme...one year it would be horse "stuff" (we lived on a ranch) then the next would be sporting goods, and so on. But whatever the theme there was always the gag gifts. Each year we would get each boy something really silly. A Barbie, a My Little Pony kite, a Strawberry Shortcake pillow, etc. ....I think they looked forward to those gifts more than anything.
It wasn't until recently my son informed me they were not fooled at our feeble attempts to be Santa but it made them happy because we tried so hard and they secretly cherished those silly gifts, not because they would ever use them, but because we put so much effort in making them laugh. What he said was a Christmas gift I'll carry forever.