If he's acknowledged the depression, then he'll either do something about it or he won't (like go to a C or a DR.). Even IF he sees the book and even IF he were to read it, the result would probably not be a light bulb going on. I know you want him to hear/read info somewhere that will help him to "fix" himself. I just don't think it will come from you (sorry).
Your plan to look good and not be too chatty sounds good. You need to work on detaching though. I know, we all say it and we even do it even though it's hard. It really does help you feel like you have some control over YOUR life (which is the only one we've ever had any copntrol over anyway).
Jack makes a good point about not involving the kids. I understand that you're not meaning to, but with smart kids perhapsm more vigilance is needed. Also, if your mom is that bad, even though they're helping you out....you might want to limit that contact. Just a thought.