It's best not to let them get too dry. A VPD below 1.0 is usually recommended. I don't point a fan at them at all, but I do keep the air moving in the tent.
I agree with the above post.
I don't let fans blow on my seedling at all, they are taking moisture from the air and the fans can get things to dry.
Later in veg and into flower I let them rustle the leaves gently but the important thing to do is keep the air moving.