What's an interesting thought on this line of reasoning is that if our brains are hardwired to believe, either those who say they don't believe religiously are an aberration on the order of dysfunction, since nature selected it for the species as a whole, or... they actually are still believing religiously because they too are hardwired for it, but they are mistaken that not believing in God as a literal being means they aren't still believing religiously. That would be those who replace God with Science to put their faith into. Hence, science becomes Scientism. It's in the genes. It's still a religious belief. Science is the Answer to our quest for Truth!
I think any developmental studies will show that children with active imaginations are happier and healthier overall.
No, not period. If they feel better, they will be healthier. Period. How we think and how we believe very directly affects our health. This is well known nowadays. If you think dark and negative thoughts all day, you make your body ill through stress and a host of other chemical problems. If you are hopeful and optimistic, it reduces all of those and you have overall better physical health, as well as mental health. So, if it makes them feel better, then everyone should desire some point of view that does that too!