Non- & ex-Christians: without ruining the Christmas spirit, how would you broach the topic of non-belief...?

... in a family setting? I've never wanted to be the reverse of what I once was (an evangelical Christian). I just want to let my cousins know that it is not immoral to doubt. (I am so thankful for the writings of freethinkers for liberating me from the suffocation of faith). It's been hard to phrase exactly what I mean... please ask if you want any further clarification. (Just want to know if anyone's been successful with all this!).