The Man Who Was A Santa Claus, by Walter Daniels

If you are not going to use the link, but want to read the book, search for it with the title, not the author name. Reason: it's listed as being by Wzlter Daniels. Now, frankly, I think Wzlter is a very nice name, and when it comes to brand differentiation, you can't go wrong with a Z. But, YMMV.

Joe loves kids. He always has. He has none of his own, but he has a reputation of being the go-to guy for stories among his nieces and nephews.
He's a nice guy, but circumstances haven't been nice to him. Cars like to hit him, and he is now mostly confined to a wheelchair. So, when he gets a phone call asking him if he'd like to have some seasonal employment, his initial reaction is to say 'Bye-Bye!' and hang up the phone.
He doesn't, of course, and you know who was on the phone, because the title of the book, right? It was Santa, the REAL Santa, the current Santa, and he's looking for someone to help spread Christmas around to children who need it.
What do they need at Christmas? Same thing you and I do. What they need is to be loved; to be reassured that love is real, and that love conquers all. It does, you know; and it might just take a crippled Santa to really be able to understand that. Sure, there are perfect bicycles in the story, and reindeer blowing snot on rude children (always a favorite) but no amount of toys, either kid toys or grown-up toys, will ever be able to work the magic in the life of a child, or an adult, that love works.
Here's a truth: there doesn't have to be an actual Saint Nicholas coming down the chimney for the love part to work out. And the people who give and receive love don't have to be in perfect physical health for it to mean something.
So, Joe gets to distribute some special Santa goodness. It's not because he was sprinkled with fairy dust (although there is magic involved); it's because of who he was, before he ever answered the phone.