For synchronizing with sound we could have a tile that indicates whether a sound is still playing. Then you could test this in a ticking script.

I'd vote for that.

I doubt that it could get much simpler if you have to start from first principles. The only way to make this usable with kids is that someone experienced builds these animation helpers, and the kids start from that project. I plan to show my ideas about this at Squeakfest:

I like the idea of helpers, it is a very good suggestion.

I look forward to your talk.

Stephen