I would have to say that my boys are probably agnostics. (Let's get that out of the way.)
But are they missing out on a vital part of growing up? Are they more 'evil' than they should be? Am I doing them a disservice by not getting them baptised 'on the chance there might be a god' and more importantly (in some minds) am I deliberately denying them a place in an afterlife?
Fact: My boys are fantastic. They are all extremely caring individuals. They share with each other and with their friends. They are polite and very respectful to other people even when they have not been appreciated for being so. They are quite altruistic and never expect a reward for being so. I am very proud of them all. Quite simply, if there are any gods out there who still think they deserve to go to a place of eternal damnation, then grow up.
My middle son has started to worry about what happens after you die and I think that we have given a balanced viewpoint. We have told him what some people believe: afterlives, reincarnation and let him think about that. What I say is that you remember people, and your life is changed by knowing them. They will have affected you in a variety of ways - some inspirational, some as a warning, some of them will be key factors in how you interact with the world around you.
When my father passed away, he had a humanist service. My boys all drew pictures to put on the coffin of happy things they remembered. As they have grown, I tell them about things my father did. They like sport for instance, which when my father was a younger, fitter man, loved to take part in. (It's in the blood, I tell them; although it seemed to skip a generation with me...)
And that is where a kind of real immortality emerges. My father lives on through my deeds and actions. I learned a lot about being a father from... my father. When I look at my boys, I hope that I will provide inspiration that will last for generations.
No mysticism, no religious 'comfort blanket', no wishful thinking, no lies...
I have told them the truth and I believe it to be a happy one. :-)