I would hope they Apple Store employees would know what to do. When I worked there, the training included a special, very extensive, portion on Mac OS X for people with disabilities. To be fair, I didn't know about any keyboard shortcut (I did leave before Panther came out), but I knew enough to direct the person to System Prefs and Universal Access to fiddle with those sorts of settings. I hope things haven't slipped so much that the employees don't even think to check that...