Oh man...I'll bet it's crazy up there right now!
You're right The elves are probably working 12 hour shifts, checking the reindeer, making any changes to the sled (checking all the harnesses, replacing bells, re-painting the sled, etc), doing any repairs/cleaning Santa's bag.
Mrs. Claus is probably already starting on Thanksgiving dinner. I can't even imagine how much work would go into feeding Santa and ALL the elves! Elves have small stomachs so that should help a little but man!
Santa is probably on his second pass over the naughty nice list, over seeing/double checking all the elves' work, checking all airport flight plans so he knows what air space will be crowded, going over his flight path to find if anything has changed (new sky scrapers, bridges, billboards, etc.), all while trying to pack on as many pounds as he can (we can't have a skinny Santa).
Ok I think I might have taken this a little too seriously! Lol