In the Christmas Special, the kids come to see Charlie Brown as right and are fairly vocal about this ("he's not a blockhead after all", etc.). It is somewhat tethered to the religious elements voiced by Linus, which gives the turnaround to Charlie's perspective a kind of cultural weight, i.e., the audience is intended to understand the kids as wrong in some kind of fundamental way. It's not as simple as "the magic of Christmas".

In the Halloween Special, the kids don't do the same for Linus, apart from Lucy who pulls him out of the cold and tucks him into bed.

The dynamic between Lucy and Charlie is a lot deeper than her cynical kicking the ball trick. Schultz uses their interactions (the psychiatry booth, him keeping her on the baseball team even though she's consistently terrible) to reinforce an overall theme that optimism is better than pessimism. Occasionally he directly peels back the layers behind Lucy's crabbiness like when Charlie's in the hospital.