Sorry to hear that Bella. Obviously not everyone likes Christmas - we all have our likes and dislikes. But children get very excited about it and your children will probably be able to tell if your DH takes a very half-hearted approach. Is he prepared to help out at all or is he leaving it all to you? Are you hosting Christmas dinner yourself or are you going somewhere else?
I guess the main advice I would give you is to start by making some lists. Make a list of all the presents you need to get/who you need to buy for. Get the kids to make their Santa lists, if they haven't done so already. Black Friday is taking place this Friday so you may be able to get some reductions on toys etc. If you're hosting, make a list of what you 'll need for Christmas breakfast, dinner etc. Don't forget things like alcohol, soft drinks, snacks etc. Decide if you're getting all your food from a supermarket or if you need to order the turkey and ham from a butcher. If you're not hosting, maybe check with your hosts and see if there's anything they'd like you to bring.
Maybe set a date to bring your DC to visit Santa. Although the 9 year old may be too old for this? They'll probably enjoy some Christmas movies or maybe a baking session - making gingerbread men or something like that. Don't put yourself under too much pressure, especially if you're doing it all or yourself. Or most of it, at any rate. And finally, tell your DH you want a very nice present under the tree.