I don't unschool my son. I was unschooled, home schooled, and attended a democratic school, which was basically unschooling at school. I'm not judging anyone, but my personal experience is radical unschooling works for most children. I know it didn't work for me, it didn't work for my siblings, and it didn't work for my parents in the long run. I think unschooling can work under the right circumstances.
Happiness is important, but I don't think it is the only measure to decide if a child is doing well and thriving. My son would be very happy playing video games, watching TV, and eating Fruit Loops.
I would be happy spending all my time reading, spending money on books, and occasionally walking my dogs, but I wouldn't thrive. I'd also be homeless, dog less, and book less eventually and cease to be happy. I have the cognitive judgement to know I need to go to work, pay my bills, and walk the dogs three times a day. Eight year olds do not have the cognitive ability to always make the choices that are in their long term best interest. I want my son to have choices in life and to me that includes making sure he has the foundation of good education, some self control, and healthy habits. I realize that is sounds very authoritarian for this forum and even MDC. My son self regulates in many areas and has, at least according to most my family and friends, way too much freedom, but there are some desicions he isn't ready to make.