Lots of good responses here.
1. If you have kids that are good and can win easily, one of the meets can be a training day. Run them in a bunch of off events. Got a good miler? Run him in the 4,8, and 4x4 then have him do a long cool down, easy tempo, tempo intervals, or some sort of supplementary session after the meet.
2. If you have kids that aren't going to win going 85%, (like most of us). Then either limit them to one event per meet OR have them take off the occasional meet.
3. Recognize that some of the best training for racing is actual racing. With very underdeveloped kids, you can race them more frequently because they just don't know how to go all the way to the well during races and won't really burn themselves out. You can comb through athletic.net and find freshmen who run 10-15 PR's per season just because they're running easy mileage and lots of races.
3a. If you're going with option 3, keep the volume relatively high, since you're going to be treating early season meets as workouts with your newbs.
4. If you fell the need to add in another quality session, especially to further the kid's aerobic development, Go with some sort of tempo, CV interval, cruise interval session that isn't that hard.
I had a 2 miler 10 years ago. He holds our school record to this day. In hind sight, I probably had him do too much hard stuff his senior year, after setting the record as a Junior. If I had to do it over again, an average week might have looked like this. (he went up to 80 MPW in the off season and was 50-60 during the competitive season)
M: 1-2 WU : Drills + 5 ish miles tempo effort + strides + short CD and Stretch/Roll
T: Sprint drill warm up + 8-10 easy
W: Dual meet day. 2 mile WU + drills + strides + 1600m @ 3200 pace FTW + 1 mile CD + 800 HARD + 3-4 cool down
Th: Warm up sprint drills + 8-10 easy
F: 4-5 easy + 4 x 200 @ 1 mile GP with full recovery + 800 CD + roll + stretch
S: Invitational 3200 + long cool down (8 ish total miles for the day.)
Sun: Easy as needed for weekly volume or Off or Cross Train if the upcoming week was another 2 meet week.