I’ve seen numerous terns charged with vandalism because they rolled a teacher’s yard. Add pesky glitter to it, I guarantee these kids will be charged. Albeit, their only punishment likely to be community service but there will be expensive court costs that have to be paid.
OP, you say it’s biodegradable dependent on the weather. You say we (I’m also in TN) gets lots of rain during summer and winter but you’re wrong. We went 10 weeks without rain and this winter is going to be a lot dryer and warmer than in years past.
Also, in regards to the statute of limitations, you could be sued up to a year afterwards for damages. I know you’re thinking there won’t be any with this case but I can’t express how often that thought is wrong. And again, there will be big expenses (court costs, attorney’s fee, etc) to come of it.
In summary, this isn’t going to end well for you and your children. They need to come up with a prank that isn’t going to potentially mess up their future.