Would you be kind enough to explain exactly what these kids are doing? I'd be most appreciative!
The kids are using the tennis balls to demonstrate rhythm. On the quarter notes they bounce what is essentially the steady beat, on eighth notes that toss the balls back and forth in their hands to the rhythm of repeated 8th notes (showing the division of the beat) and with half and whole notes they are bouncing on the beat that the note starts. Hope that makes a little more sense. I lay a piece of moderately fast music for them to work with like "Let's Get it Started" by Black Eyed Peas or "Stars and Stripes Forever" by John Phillips Sousa.