Congrats! Good questions.
Christmas time is slow in Vegas compared to all other times, so you will have better selections of what you want to do. That said, that time of year many shows are on holiday so the selectionns are smaller. As to the shows, I would wait and see how you feel when you arrive and go to the 1/2 price ticket places to see if there is a show you may want to see. (Depending where you are staying, one in the Coke shops, fashion show mall and other areas)
As to gambling: Where are you staying? Many hotel offer free classes in the mornings for table games. You learn and play blackjack,craps and other table games. Slots are slots! Either tables games or slots it does not matter where you gamble, you just want to have fun. If you want lower table stakes you have to get up early for $5 USD- tables at the "posh" casinos because they raise the limits in the late morning or afternoons. The smaller casnios retain the lower limits all day.
Free shows will be in the afternoon, a magic show or two. Maybe a 2 drink minimum. Big Elvis is free, only play during the weekdays after 3:PM and worth going.
Christmas Dinner---Again that is up to your taste. Many are running on a small staff, so find a place when you arrive and make reservations. Steaks- NYNY, MGM and Excal have nice steak places on that end- Range in Harrahs is okay. Circus Circus great Steakhouse and Hugo Cellar downtown is great. Others you really can not go wrong with a named Chef. Ask the Concierge when you arrive, they will assist you.
Again enjoy and congrats!
