I feel overwhelmed a lot too. I don't know exactly what type of mindfulness books you would like, but a Buddhist publication that has helped me out a lot is the magazine Shambala Sun. It's much easier for me to read and think about a complete article right now, rather than process an entire book, so the magazine format works well. The articles in Shambala Sun are always well written, and the majority of them are thought provoking and often funny. My friend sent me a subscription for Christmas one year, and being a lapsed Buddhist (i.e. I haven't sat in meditation for several years - we have three children 9, 7 and 2), I didn't know if I would like it, but it has been wonderful.
We're also a homeschooling family, and one thing I find that helps out a lot is to go places. Staying at home is nice when I'm feeling organized and happy, but if I'm feeling overwhelmed or depressed, everyone is always happier if we spend the afternoon at the river or a friend's house or go to the library. I think it has something to do with the fact that our house gets so extremely messy with three kiddos running around....
Another thing that helps me a lot, if we are staying home and I'm getting overwhelmed, is making a list of all things I want to accomplish during the day. Even if the list includes seemingly banal things like making peanut butter sandwiches for lunch, or reading Goodnight Moon to the little one before bedtime. The list helps me keep a rhythm in our day, and it makes me feel less overwhelmed.
Do you have any other SAHD friends? I always wonder if the SAHD in our homeschool group feels isolated and wishes for more male companionship. Do you know any older or retired men who would enjoy spending time with you and your children? Neighbors? Every morning, my children and I go for a walk with my father and sometimes my mother, and it seems to set a positive tone for the day.
I hope that helps. It can definitely be tough to be a stay at home parent.