I'm aware of screencasting tools, though that would add a layer of difficulty and distance that I think would keep the kids from being able to do it autonomously.
If Processing well and truly has cut out video capture capabilities, I may just keep the tool as-is (as a performance 'toy' rather than a video creation tool), and perhaps later try porting it to a similar but more powerful system like OpenFrameworks (if that can do video capture - I honestly don't know).