See if you can get every kid a recorder to play on that is halfway decent. I'd look on amazon for canto recorders that are $4.50 each. They're decent for the money. You can find a ton of free materials online for the kids.
We also spent time using music theory.net and doing examples together or of they have chromebooks they can do a note name exam.
Other things you can do with the kids is use rhythm bee. It's only $100 for the whole year and has been wonderful to teach our kids how to count. We start them in 4th grade with rhythm bee and don't go super deep, but just reinforce the basics to get them understanding rhythm confidently. Quarters, Halfs, Wholes, Eighth Notes.
I use rhythm bee all the way up into high school band but they learn most of what they need to know in junior high.