I would speak with the school. The assistant Principals will have the resources to advise with what needs to be done to help your sons get back on track. they have the resources to help in your situation..
Please allow me to remind all parents. The counselors in High schools are mainly academic counselors. A few have degrees in psychology, but their main job is to make sure the kids are on the right academic track.. not always personal problems. Yes, they can speak with a student about personal problems and suggest help, but getting the kids to just graduate is their goal.
In elementary schools the counselors are there to figure out learning differences for the students that struggle. Same in middle schools. Making sure the students have their academic needs are met. They are not always traditional "Counselors".
Ask about alternative school in your district.
Some students are so over following the "school regiment". They are ready to just do the work and get out.
In our school district there is an alternative high school that allows students to go at their own pace. As fast as they want or as slow as they need. The students picks their schedule. For example. a student may still have social studies and chemistry to graduate.. Essentially each of these courses could be completed in less than 2 weeks, if the student attended this school for 7 hours a day for 5 days straight.. only working on one subject and then passing the final exam..
These students may need to support their families, may be burned out, may be ill, may be pregnant, but this is a way for them to pick their graduation path. There is the minimum, and then there is the college track.
Find a therapist to work with al of you. I am going to guess, they were and still are completely freaked out about your health. They are trying to ct strong, but still need the stability of a parent who stays after them.
Always be honest about your health the prognosis. Let them go to the doctors appointments so they will know you are not hiding information from them. They want control and right now all of you are not in a situation you can always control. they are frightened. Never underestimate your children. They can handle the truth better than just imagining what is going on.
I am sending you strength and peace. I will keep you in my thoughts.