Orlieborlie, I think it's an excellent idea.
Guy I used to work with did something similar. He'd worked all over the world and restricted his Christmas cards to those people in far-flung places whom he never saw. Said he saw his work colleagues every day and it was just as easy to actually say 'Happy Christmas' to them. Instead, he just posted one card on the staffroom noticeboard, and one on his classroom noticeboard for the kids he taught.
He would then donate to his chosen charity (a neonatal unit, I think, 'cause of his twin daughters). No one objected at all.