Welcome Bobz,
Yes, December is one of the best months to have a trip to Thailand and Kata Thani is a very big and good hotel. Never staid there but I have a couple of friends who did and it was really nice.
Forget to book for all inclusive and have your meals outside, it will be cheaper, you will meet more people and it will be really good. You will find many little restaurants everywhere, all of them are good and a dish will cost 80 bath (1.5 €) instead of 600 bath in the hotel.
Many things to see, many places and people to discover in Thailand, don't miss it while staying in your hotel
BTW, congratulations
