It sounds to me like you are doing what you can and balancing things the best you can. You have to take care of yourself as well. Don't take the guilt trip -- you have enough real concerns.
As for parents, I am one, and I believe I can speak to that. Moms can put real guilt trips on their kids. It's not just about the cancer, it is the attention they want. When we put Lucie's mom in a nursing home, I told Lucie to decide for herself what she thought was the right frequency of visiting during the week. Because, it would never be enough for her mother, no matter how much she did. She found that to be true, and she had no siblings to help out. I loved my mother-in-law dearly, but I could see a real trap for Lucie and warned her ahead of time. It worked out fine. And, of course, I vsisited some with Lucie, and some on my own. My visits (I wasn't a blood relative) were always enough, but Lucie's never were. Just the way moms are. Give yourself a break. It sounds like to me you are very compassionate and doing what you can. Don