We didn't do the Easter Bunny or those Elf on the Shelf things, but Santa was part of our Christmases when the children were small. I wouldn't have been pleased to have grandparents pushing their ideas though, and wouldn't do so if my children decided not to have Santa in their lives.
Families have different traditions even when they include the Santa myth. My mum used to say that adults sent their presents to Santa, who then brought them down the chimney, and my ILs used to say that one present was from her and the rest from him. This was closer to our take on it, which was that people could give (and get thanks for) their own presents, and we did the same but bought extra from the man in red. There has to be one story if children are not to get confused, and IMO that is up to the parents. Grandparents have had their turn.