Here’s one I’ll add:
The program is called Kidpad, and can be found here:
I saw a presentation delivered on this program on Google’s YouTube space. Here’s the link to that:
It’s a very interesting program, and may or may not be useful for this type of video, but it is surprisingly powerful and intuitive, and it’s free for non-commercial use! (I have no clue what they charge for commercial use.)
I’ve not used it enough to know if it would work as well as the other solutions listed here, but if nothing else, it’s fun to look at.