First of all, please accept my condolences. It is so horrible to lose a parent and then to lose them close to a holiday makes it worse. I lost my father the day after my birthday and birthdays haven't been the same since. But, I do have a peace about my Dad because he, too, loved the Lord and I know I will see him again. I think this helps more than anything...the knowledge that you will be together again. My husband died suddenly and that thought kept me together.
First, you need a good cry. The sadness can build up in you so you feel like you are going to explode! I usually do my crying in the shower and feel a lot better when I get back out. The stress and tension has diminished. Please know your whole family is sad about your father and I'm sure there will be tears tomorrow but that is fine. That shows how much you all love him. Notice, I use present tense. I believe he is very much alive...just his method of transportation on this Earth died. I'm not trying to be "preachy" and I hope I'm not offending you or anyone else but, from what you said in your post, I think you believe this way too. But, when you are grieving, you don't always remember these things.
Tomorrow morning, remember why we celebrate Christmas and take it from there. You will have your loved ones surrounding you and I think this really will be a big help to you. You probably will share some stories about your father that will bring smiles as well as tears but this is all a part of grieving and every one of your guests will be grieving, too. You will not be alone with those feelings.
I'll be praying that you have a far better day tomorrow than you think you will right now. A lot of planning has gone into your Christmas celebration and it will show tomorrow. Enjoy your family, enjoy the children, and know your father is having the greatest Christmas celebration of all!
Sherrine