Ultimately in the end, it's up to you and what you feel is best.
It's not uncommon to fear sleep because of seizures. Been there, done that. It's hard to sleep when you're afraid of having another seizure. It's nice to be awake and think, "I feel okay right now. I don't feel like I'm going to have a seizure." With sleep, that can change sometimes.
I'm not certain if 4 a.m. has been the norm for you because of schedule activities, insomnia, or if it's become a schedule that has settled with you. If I went to bed late and got up at 4 a.m. every day, I know I'd be miserable. I try to sleep in when I can and it helps if I can be in bed by at least 11 p.m. or midnight. Although, I could sleep from 11 a.m. to 3 p.m. the next day and still feel tired so insomnia isn't my problem. For whatever reason, I'm always tired and not resting well, even if I feel like I didn't have a seizure in my sleep. It's important to get more sleep when possible.
Is the worry also that the Christmas gathering is late at night and then not getting enough sleep and waking up early? If that's the case, is it possible to move the gathering to a day they may not work? Or scatter it a bit, hang out with children and grandchildren at more decent hours on their days off or when they have a break in the day for a few minutes? If the worry is the late night and waking up early in the morning, the meeting sounds like it'd be late regardless of virtual call or going in person unless you're able to get into bed and sleep in until later.
If the need is rest then perhaps you could explain that you've been having health struggles and you have to get to bed at a decent hour or get enough sleep?
Perhaps you can stay at home in your comfort zone, and have others come to you to visit if possible? Then, if you need to go lie down you can and you can make sure that one of the kids locks the door on the way out and returns the key the next day or something of the sort?
Perhaps there may be a belated way to celebrate this when things might be a bit better?
I've had gut instincts that told me I should or shouldn't go to places. At times, these gut instincts were right and other times, it was wrong and I regretted not being there, but would still try to tell myself, "Maybe I was better off because I was home. Maybe something bad would've happened had I gone?" and of course I could never be sure. I try to get out when I can and go to gatherings. If I feel a little off or weird or like a seizure is coming on, I tell my husband and be careful and usually excuse myself to go home as I'm not feeling well. Sometimes I'm glad I've gone to things either way, even for a time.