Very valid concerns you have. If the mark comes in during our lifetimes, it's going to cause some mega-complicated and literally heart-breaking situations.
From my point of view, I like the idea of pre-preparing and heading for the hills when satan's kingdom finally gets the whole world under its control for a short time, then seeing how long I can evade the new world order, if it's even possible to do so given all of the technology they no doubt have to monitor the whole planet.
Then again, this is a completely unrealistic notion because it's not going to be fun at all. It will either be 'take the mark, or die'. (Matthew 24, verse 9; 'Then you will be handed over and put to death, and you will be hated by all nations because of me.')
Families will be literally ripped apart; (Matthew 10, verse 21; 'Brother will betray brother to death, and a father his child; children will rebel against their parents and have them put to death.')
I really feel for you, especially given that you have children that are no longer under your roof. I unfortunately am not in the position to offer you some sound advice at this point, but there is something I would like to share with you.
For what it's worth, I am a close observer of what the globalist agenda and new world order are up to. World leaders that we see on TV are only puppets, there are secretive groups (such as the Bilderberger group) over them, pulling their strings. These groups control governments (including ALL western countries), control all mainstream media, all major banks, decide on all wars that western countries get involved in (generally based on lies peddled through the media), and so on. Their ultimate goal is the one-world-government, satan's kingdom.
I am telling you this because the same secretive groups appear to have an agenda to eventually 'microchip' all people (I believe I have covered this in an earlier post on this forum). I am only a mortal person who has limited knowledge, but it is possible that this could turn out to be the mark of the beast. Only, the media won't market it as such, of course, it will be marketed as cool, like so many other of the latest gadgets.
If, and I emphasize the 'if' part, my judgement is correct, then the mark of the beast is still at least a few years off. The anti-Christ, who most biblical scholars agree will come out of a reformed Holy Roman Empire, most likely a revived European Union superpower, first has to come on the scene, and so on. I hope my judgement is right, or perhaps even conservative, in that you will perhaps have adequate time to educate your children on these matters some time down the track, before the mark comes.
Anyway, God bless you. I will pray for you that The Lord will somehow see to it that His will be done in the lives of all of your family, including your children currently not under your roof. God bless.