Went though something similar with DH. Has adamant his mother would be guardian, he was such a mummy's boy and he had his mother and her parenting on a pedestal. I wanted a friends who were closer to our age to be guardian.

Eventually he came around to the idea. I really promoted the idea that Grandma should stay Grandma and that she can be still very involved in the girls lives. I think the role of grandparent is important and more so with the loss of parents. Also his mother had been ill with bowel cancer and I think he began to see that maybe she was not the best choice. He has spoken to her about out choice of guardian and why we have chosen her and her family (she is a BB member so wont say too much ). Thankfully she understands (well she did at the time, she is going a tad dotty so hopefully does not forget)