Hi there!! Well first off we as parents tend to tie things unnecessarily to certain events thinking they have a profound effect on our kids - when they don't neccessarily - point in fact a friend of mine is having difficulty with her son. He was recently diagnosed with clinical depression... But prior to that she was blaming her self, their home life, the death of a family member (he was very very close to - a 22yr old cousin who was like a dad to him) the lack of his father in his life etc. prior to him going to see a counsellor she wrote down a list of what she thought were life changing events for his dr to take a look at. He went into the session - came out and said to his mom, when did this happen etc... He didn't even remember half of them. I think the possibility of losing a parent is traumatic, two out of three of my kids were living at home during my diagnosis and treatment. They came to see me in the hospital, they were there the day of the surgery. My youngest who was living at university came home two weeks later during reading week and we spent a week in Mexico as a family. I kept them informed about what's going on, on what the dr was saying, but it's hard because seeing you doing okay makes it harder for them to fathom loosing you. I want my kids to be happy and enjoy their lives - focusing on the time we have together and the good things. They know I could have a recurrence and be taken from them - we've never hidden what was going on from them - an I've always said a diagnosis of stage II can be as deadly as easily as a stage IV could survive (i have a friend right now in clinical trials, for peritoneal cancer - she's close to our family - my youngest's god mother - they've dropped in to see her, and say hi asked how she's doing etc... They arent afraid or in denial, but do live their lives they way they should. I would never want them to stop their momentum for me because of whats going on. Yes I've struggled with cancer, but - I could also step off a curb tomorrow and be mowed down by a bus. So could anyone... So I wouldn't focus on the what ifs with them, it's next to impossible for them to imagine, and frankly unless faced with the inevidible - a terminal diagnosis - why push it. Acting out is what teens and young adults do. It may have nothing to do with your previous diagnosis. I'm sure they've been affected by it but you're fine now, so they are treating you like most kids would - a parent... Focus on the good, and being close as a family, give them good things to remember don't let cancer be the forefront of your life, it's there, it's a part of it, but dont give it that much power, don't dwell on what ifs, don't try to hammer that into their brains, you can't force something like this onto another peron. Plus why would you want to?
If you're feeling down, and burdened by all that has happened go talk to someone outside your family. You need to unload, and sometimes verbalizing to someone impartial will give you the feedback you need to move beyond it.

Good luck!