We never told our children there WAS a Santa - we ALWAYS said he was pretend. Made the aunts and uncles mad.
We did the same thing. Really ticked my niece off when my son told her daughter Santa wasn't real though, so I had to threaten my kids with having their presents taken away if they ruined believing in Santa for those kids whose parents did lie to them about it. LOL
I didn't tell my kids Santa was real for that reason. I would sometimes act like he was real, but sometimes I would just ask the kids if they thought he was real or make believe. That way if they aren't ready to give up believing in Santa, they don't have to, but if they are ready, they are proud that they figured it out for themselves.