A question for Brith Mothers about sharing information

Recently we sent our yearly update about our 10 year old son to his birth mother (he was adopted at birth). We have a semi-open adoption, which for us means that we have each other's email addresses, and email a few times a year, sending pictures back and forth occasionally. No visits, no identifying information - well, not much, we're not super careful about it, because we' don't have boundary issues or any concerns about his birth family. Near his birthday, we send a longer letter - a yearly summary, with several pictures.My question is, what is not okay to share? Would you want to hear about problems and concerns? Especially if you are not directly involved in your child's life? Our son has behavioral issues and life has been really hard with/for him the past couple of years. He has been diagnosed with ODD and ADHD - with Oppositional Defiant Disorder being the most trying for us. When we write our letters, we write honestly, but only write the good things: what he's up to, what he likes, what sports and activities he is doing, fun stories and good experiences. I feel like that is not totally honest, as life is really, really hard. He is defiant, lies, steals and has outbursts that leave us emotionally mentally and physically exhausted. He is a good kid. He wants to be and do better. He sees a therapist, and he is trying, but it is hard for him to get himself under control. I added a vague reference to that in our yearly letter, that he is struggling with some behavioral issues and having a hard time, but my husband took it out. I told him I didn't feel the letter was honest without it, that it was sugar coating our life, our son's life. He responded that it was not her business (not in a mean way). That she doesn't see him, doesn't interact with him right now, and it wouldn't help her to know these things. It would just make her worry. He is honestly a great kid, and has a lot of talents and great things going for him, and my husband says that these are the things we need to share, not the negative.What are your thoughts? I don't want to paint our son in a negative light. And my son only wants good things said about him - wants his birthmother to think he's perfect, but I feel like I am lying to her - a lie by omission. (BTW, his birth mother is an emotionally healthy and mature person, and a mother to other children, so she knows kids aren't perfect.) :)