I've got a copy of OS X 10.2 (Jaguar) CD 1 and 2 here that I can send you, which should run fine on either machine. 448MB of Ram should be okay, but OS X is a ram hog. I'd try to get at least 256 into the iMac, but 512 may be a lot better.

The suggestion about Linux is a good one too. It really depends on what the machines will be used for. If they are to be donated or used as light internet, email, word processors, I'd be inclined to go with Linux. Most Linux distros will be more efficient and less ram hungry than OS X.

BTW, if you have not used Linux before, it's not difficult to try it. There are many Live CD's you can download, burn and run on the machine to try out the OS without having to install. The major downside of Linux for me has been lack of wireless support out of the box. But installing on the B&W or the iMac with an ethernet connection should be a breeze. I'd suggest Ubuntu as a Linux distro, if they have a PPC version (as opposed to the more popular Intel versions). It's one of the more popular distros out there. http://ubuntu.com

PM me if you'd like me to send the OS X 10.2 discs - no charge.