How do I undo what’s been done?

Sorry this is long...

Background:  more than a few years ago when I first came out to my mother (I was still married, trying to make sense of what it all meant, how it affected me, my now ex-wife and children) mom came to see me from Texas at my request. I wasn’t sure how I needed her at the time, but asking her to “be there” was all I could think of. That request turned nightmarish, she projected the entire experience onto herself—she always loved making things about herself—and in true fashion before heading home and in a ditch effort to ‘rope me back in’ told me to leave everything, my wife/children and fully return to the LDS church, an ultimatum of sorts. 

I reacted the only way I could at the moment--that she had no right to ask me to do anything,  that she was a dangerous person, she always made things about her, manipulated people into doing what she wanted using whatever means and ways she could (there’s stories I don’t even want to write about). I told her I didn’t want her anywhere near my family, I wanted no contact until I felt it was safe for me to do that. It took a few months for me to feel comfortable talking to her again, slowly and very much at a distance. Additionally my ex and mom never really found any common ground, not having to deal with each other was/is probably 85% of my problems being solved so I don’t think my ex-wife really has many courteous things to say about my mom.

Coming out fully a few years ago, I explained to my mother that I wasn’t seeking any kind of approval or permission. While our relationship has sort of improved at a respectable level, I never supported any kind of reconnection with my two kids, in my mind I kept seeing her manipulative ways with some of my nephews and nieces so in sort of a selfish way, I protected them from her—I don’t know if cancer has made her reflect on a lot of things—maybe because I don’t see her every day, but she seems to have calmed her ways—perhaps not and it just seems like it to me. 

Recently my sister made mom a Facebook profile and requested to have my kids added as friends of hers. My kids’ reaction to that initially was “mmmh, not now” which I think is fair. I saw some of my son’s postings about it, he feels she has not made an effort to make contact, get to know them; she’s apparently kept in some kind of contact with the other grandchildren. Yes they’re resentful, but a big part of it was my doing—and I admit it is my fault—I don’t know that their relationship would have gone sour or improved had I not explicitly asked her not to contact them. She is not even on Facebook that much that I can tell, but I honestly don’t know what kinds of things reconnecting them would cause, positive/negative ones? She does ask me about the kids on our phone conversations and I talk in generalities to both.

Gaaaaah, this has gone too long already--if you're still reading: I’m a little torn, but I’m willing to accept my share of blame in causing much of this, I just don’t know if it is now too late to fix it. She is 71 so it isn’t like we have all the time in the world to see what happens in the future. It’s a mix of guilt and wanting to get this resolved ASAP. Maybe I’ll talk to the kids, do some explanations and see what evolves from that—the thought has been in my head for a few weeks. What if anything can be done at this point? Is it my job to intercede, explain, resolve? Do I drag the kids to Texas in person? Do I leave it alone? So much I don’t even know where to begin.... thoughts anyone?