No, you won't trigger a loss of trust if you do it the right way. This year, my 7-yr-old, for the first time in his life, asked me clear questions about Santa and all this stuff (we had more of that going on). Having been asked a clear question, I of course gave him a clear answer.

First he was sad - he liked the world of Santa, little gnomes hiding sweets for him in the woods when we were out hiking, things like that. But my clear answers just confirmed the suspicions he already brought home from school.

Then we talked about how this was a nice game adults and older kids play for the younger ones - and he got that immediately, kids inherently understand (and like) role playing games. So now he's in the role of those who know and play the game for the younger kids in our broader family - and he's proud of it :)

Before that happened, I actually was afraid and unsure about how to get out of this storyline without breaching trust. But it all played out smoothly.