This one got a delighted laugh from Emily, so I know it's good.
I discovered tonight that Emily's BlackBerry Pearl will play AAC encoded music (not FairPlay, just AAC). Who knew?
So I re-enabled disk mass storage support in the BB advanced options, reviewed the warnings from Mark/Space about USB mounting and told Missing sync for Blackberry to sync my new "BlackBerry" iTunes Playlist. 
Worked like a charm.
I absolutely did not turn The Beatles "Any Time at All" into a ringtone for her Pearl. I know that would bring Homeland Security to my doorstep.
Now I'm ordering a 2GB Micro-SD card and a 2.5mm to 3.5mm stereo out converter cable. Emily will be able to play the kids audio books on demand from her phone. Using the speaker phone if necessary.
 Ok, one more complication. Our iTunes music library lives in my Public folder on the iMac server. Emily has to sync the Pearl with her account. The solution is easy. I configured her iTunes to reference tunes in place, not to copy them. Then I dragged my entire music library on to her iTunes Window. Ten minutes later she had her own access list suitable for sync to the BB. Of course it won't stay in sync, but I've done this before. I just need to periodically delete all. (Actually I've done much more complex things before ...)
Update 12/30/08: Be very careful. Missing Sync stores the iTunes on your phone's main memory area -- which is pretty damned limited. If you sync infrequently, the "leave at least 5MB" default setting can start to become small, with very bad consequences ...