The omission of information is only a "lie" when truth/disclosure is owed. You don't owe your readers the full story, much less parts of his adulthood when the book is about his childhood/youth. Also, hopeful is the best you can be when things aren't going well. Optimism isn't a lie as long as it doesn't become (self-)deception in the face of clear signs that the situation is hopeless. My educational background is similar to your son's and so is my resummť, and I recently realized I am autistic myself. But, while 35 now, I did manage for the first time to hold a respectable job at a huge company for more than a year. So it really can get better, and there is nothing wrong with being hopeful for it.