I have kept out of this thread, because I still don't quite understand what it is you want of us.
Is it a philosophical discussion of the relationship between one generation and another?
Is it an analysis of the underlying psychological hang-ups that make each generation wary of another?
Is it a search for others who have had the same experiences as you have and who approve of the way you deal with them? Is it a search for a better way?
It seems to me that your therapies (I note that you have tried multiple therapies, that probably indicates that you were unsatisfied with the results) have not completely cleared up your anxieties. I think you are now airing what has been said to you during those therapies to a sensible and sensitive group of "ordinary grans". Perhaps you are hoping to "lead the discussion" to form the "right" conclusions ?
But no-one is inside your mind - or, more importantly, your heart. All the therapists and advisors in the world, and all the jargon and theorising of psychology and psychiatry, can only produce generalisations about the average human experience. Jawing can't take the place of experiencing. Other people's relationships are not your relationships. And intellectualising doesn't automatically build healthy relationships.
The same applies to your husband and children. They have their own contacts and links with your MiL - their mother and grandmother. You are not the supervisor and arbiter of their relationship with her, and whether you want them to see her or avoid her has no relevance. If the children are young, then they probably see her in company with a parent, but as they grow older they will have their own links. They may like her as little as you do, or they may like her far more than you do - it is up to them and it is certainly up to your husband - her son - to form his own relationship and see his mother as and when he wishes.
But, of course, your own attitude may be that their inclinations come second to yours - if that is so, you are in for more problems as your children become adults.