Dear Sam,
You worked so hard to stand on your own after leaving that it makes me sad to hear that you're thinking of going back, even for one meeting.
If you go with a DF'd friend, it seems that you are supporting and promoting the borg as the right place to be.
Please ask yourself why you are really thinking of going because it sounds like the friend is an excuse. Ask yourself what positive outcome there might be? I see nothing but negative reactions from your daughter and son, and your mean-spirited ex, and as someone pointed out you'll be used as an example of how miserable ones are that leave--they can't be happy and have to return.
Not something to be done on a lark, methinks.