My mother made the same decision you are contemplating. She explained to us the rationale behind her decision and over the years since her death, the entire family has held her up as a hero. It was great to have HER with us for one last Christmas and that's what we all remember. You and only you can make the decision about the quality of your life. I'm sure you have a bucket list. If that's what gives you quality, go ahead and do it. Your family will come to understand.
Keep it positive and smile:)