He really emphasizes that if you're going to believe in something, it better really be true not just "worth believing in" or "virtuous" or "helpful" -- he himself could have written Belief in Belief.

One gets that impression if one reads Mere Christianity and the Screwtape Letters. But if one reads his works aimed at children one gets the impression that he wants children to believe despite evidence. See for example the scene in The Silver Chair where the protagonists are trapped underground and the Lady of the Green Kirtle tries to enchant them to think that Narnia, Aslan and the Sun are all things they made up as part of a game. They are almost taken in until they declare that they will believe in Aslan even if there's is no Aslan because the world they've imagined if it has been imagined is a better world than the one they live in.