I know where your coming from a little dude. I lost my grandfather on my father's side a few years ago to cancer too. He was always kind of an asshole to me because he hated my dad and thus hated anything to do with him i.e. me. The rest of my family didn't really care as he was quite rude to them as well and I only have one uncle and two cousins on my father's side. I was able to spend a few days with him during his last week or so and it meant a lot to him and me. I wish I spent more time with him when he was healthy because he lived a badass life. He owned a pizza place, a printing company, a crab cake shack that allowed him to travel the country (Captain Jim's). And he helped out so many people in need, donating much of his money to charity, volunteering at various suicide hot lines, and even letting homeless men live with him. I was far more crushed then I expected to be and it took me a while to get my grip back after his passing. I spent everyday after school with my grandmother for about two months after he passed, I don't even know why, just felt right.
I'm sorry this has happened and you can't have direct contact with him. Hopefully you'll be able to see him at Christmas as you said. My thoughts and prayers are with you. Good luck.