My daughter is in remission from leukemia and was in chemo from 3 to 5. If it was all-b then I wouldn’t worry much. Yes, you’ll have some dark thoughts along the way. I still do at times. But they’ll fade away as your son goes on to lead a pretty normal life. My daughter is 10 now with passions for MMA and horse riding which took a pause because a horse stomped on her toe this past summer pulling out a nail. Was an accident and we treated it like one.