First, I am so sorry for your loss
Second, I don't think you are wrong to expect/hope for more from your family. It's both a natural and reasonable expectation that they will visit for longer than a few minutes at a time and keep the plans they make with you.
I agree that the best course of action is to confront them bluntly. "You're my mom and I'm going through a tough time right now. I need you and I need to feel like I matter to you. Is there something about my home that makes you uncomfortable? Is there something I can change there that will make you feel like you can stay for longer than half an hour? I feel hurt. I love you and want to spend time with you."
And I would also lower my expectations. I'm not sure why your family is this way, but this is who they are and unfortunately, they may never change. But also know that it's not a reflectation of you. It's them. Seek the familial relationship
with those you know have the capacity to be there for you as much as you are with them. DH, in-laws, friends, etc.