I wouldn't rule out that Mexican Black King just yet. Kings are awesome snakes and definitely a great snake for the kids. And seriously, how gorgeous is the MBK?? Plus, obviously tons of other awesome King morphs. Ok, so maybe I'm a bit biased because I love Kings. That being said, you like the frame and bigger heads of the BP but want something a little different... A Hog Island Boa would be great, maybe a Childrens python might be nice maybe a carpet python if you go male and stay away from coastals (I believe the others tend to be smaller, but maybe an Irian Jaya like Shane said?