Wow, extremely polished game jam entry - this is very impressive stuff. The art and sound are very polished, the mechanics work well and the interface is clean.
The gameplay feels very arcadey - and works the way it should, but personally I found myself mostly spamming a lot of stones in a row blindly hoping they would hit somebody - as the game gets a bit hectic with multiple enemy kids. Not sure how I would fix that though :)
Thank you also for providing the source code, I have already had a look and will be sure to dive deeper into the code of someone clearly significantly more experienced in Lua than me!