Responding to the original post:
I don't know how to say this without offending - it's not coming out right in my head, but take this in the spirit it's intended.
As a son with a mother in your situation, but less sure of herself...
It's much easier if you decide before you get into this type of situation what you are going to do and just stick to it, at least for the kids.
We are trying to start our lives, and IDEALLY (and whose life is ideal anymore?) this would not be an issue at that point. In a perfect world, grandparents would visit together, kids in their 20's wouldn't be worried about going to their parents' weddings, if they were getting taken advantage of financially and otherwise, etc etc.
This is coming from a guy who is seeing his mother waste that last 10 years of her life on guy after guy, just HOPING he's interested, mooning, being a "good friend" but always hoping for more, but never getting it. I just wish a decision could be made to be single or to be looking, but not this in-between stuff.
I know this is very one-sided, and everyone deserves the right to be happy. So just take it for what it is...one-sided
And good luck either way.