I am being lazy, so there won't be quotes, but the first post of this thread you commented on your Inlaws lack of connection, lack of reaching out over the course of your marriage. That is their pattern of behavior. Sad as it may be.
In your last post, you talked about your parents and how THEY reached out to their XSIL. How THEY maintained the relationship with their grandchildren. That is their pattern of behavior. And it is admirable and wonderful. Just a little unusual.
Unfortuntately, because you are dealing with a difficult at best MIL, facilitating the type of R your parents wanted with their grandkids, is going to kill you.
You don't have to be a barrier though. And that takes no energy. You pass along messages, you make sure the kids have the phone numbers and addresses, you encourage them and the R (unless you feel they are being damaged by the R), you say NOTHING negative, you listen, listen, listen to your kids...
And if they ask you to drive them somewhere to meet grandma, you do it.
Now if YOU want a R with your inlaws, that is up to you to make the effort. Just don't use the kids as the excuse and be prepared for them to not respond.
Now, to relieve some pressure, can anyone else take S12 to the boyscout thing this weekend?
You are doing too much and you are going to end up sick or worse. You need to SLOW DOWN. Even if it is just for a day or two. You haven't stopped since you went to Florida.
"Acceptance doesn't mean resignation. It means understanding that something is what it is and there's got to be a way through it."--Michael J. Fox