As soon as I asked if Santa was real (at 5 yr old or so), I got the truth. This made me happy. It may have helped me doubt and later leave the Mormon church at 12 yr old; it at least didn't hurt. I've always enjoyed xmas (minus shopping). I probably would have enjoyed it if I'd never heard a Santa story from my parents, but I do have a fond memory of really believing the cookies+milk would be consumed by Santa (4yr old). They definitely played pretend; they just didn't lie to my face when directly asked.

It's valuable to have at least a few people you really trust in your life; while it would be sad to throw that away in exchange for nothing, a Santa-type fun story (presented without "this is a false story ..." preamble, but readily owned up to) won't do any lasting harm.

There are real difficulties in establishing deep trust. Fun little teases like Santa (if not taken to extreme) are the least of your worries. The hard work is elsewhere.