Ravengirl, I really know what you mean
I'm on the other side, the one who was diagnosed with cancer. My husband, I could tell, was trying to be strong for me. But I knew that inside he was REALLY devastated and didn't know what to do with himself. Since he isn't close to his parents, I had him talk to mine - all his worries, everything that he couldn't talk to me about because he had to be strong for me.
I told him it was ok to not be strong every once in a while. We are only human. I know he was just as worried as me. I think I was in a better position to "not be quite so strong for" than your husband (no surgery, etc for me), but really I think you need to rely on family members as well for support.
And as far as dieting, this is what I did when I was diagnosed and the shock wore off - I maintained. For months. Until I was ready to go back to losing. It was better than gaining it all back and letting all my hard work go. My diagnosis actually made me see even more how important it was to get healthy.
You'll be in my thoughts for a while, I am sure. If you need a shoulder, just send a PM. I also know ALL ABOUT all those doctor appointments... sometimes I just felt like a human pin cushion!
Edit - I just saw your response and read it again. I think you should also get your daughter some counseling. I don't think it is good to pretend it isn't happening. And don't forget, that you can't be strong for your husband if you are in horrible shape yourself. MAKE time to see that counselor yourself. It will benefit your husband too, I guarantee since he will know that you are taking care of yourself as well.