My own MiL was a real diamond. I was lucky to have her, if only for 9 short years. Now that my eldest son is married, I pattern myself on her;
1-My son's first loyalty now is to his wife, not to me.
2- I know that am blessed that he has found a lovely woman to love him and who wants his happiness just as much as I do.
3-In the event of a marital spat, my job is to stay out of it.
4-If my son comes around to complain about things at home, I will send him right back to her to work things out.
5-I tell my DiL how much I love her and how lucky my son is to have her.
No grandkids yet, but we were told over the weekend in an oblique way that they've been trying 'for a while', and DiL is getting worried. I kept my gob shut, asked no questions and offered no advice. Just said that I love them, I'm sure things will be OK, and if there's anything I can do or if they want to talk, let me know.
It was quite hard, you know, because DS1 has always said he didn't want children so I was quite surprised and full of questions!