I am happy to say that his actual letter was comforting. Grandma Sheila did tell us the funniest thing–they bought the kids a sled for Christmas anyways, before they ever knew Carson wanted one, so that works out nice. He does still talk about it, so he will be stoked. Here is what he told me his letter says:
“Dear Santa,
I was looking for slippers and you could give me some slippers. The end.”
So that problem was solved with Grandma Sheila (thank you!) and also him forgetting to ask for a sled in his letter!