The led's look good, and maybe you should order two, just in case one fails... The timer sounds like a good idea, also, i didn't quite catch if you where gonna have the kids come in with their respective groups, but maybe assigning one to be a time keeper, would be a good idea... Also, since it's only a buck, and could be used for other activities as well. Again, the LED you picked should be fine, but some input from someone else would be nice... also, keep a look out for a cheap red led, at the dollar store, you might find one. I saw another red bike LED, which seemed to actually have a red LED instead of the case being red, but i don't know, i comes all the way from china, and doesn't have the best reviews. Anyway, you should be all set.