I have a little experience with this. About 10 yrs. ago I opened my mouth and got myself into doing a rock build and fly with my then GF's, son's scout troop. There were about 16 of them and they ranged from about 7 to 11ish yrs. old. We made it clear that this was a parent and child activity. No kid was doing this without their parent with them. I wasn't going to be responsible for some kid stabbing himself.
After looking at my options I settled on the Alpha III and the Sky Writer kits. We ended up with 12 of each and let the kids pick which one they wanted. I also bought a Maxi Alpha III to build for a Demo flight. I recommend that you stick to ONE DAMN ROCKET.....!
The first thing I did was get the parents together and held a little work shop with them. Broke the parents into two groups and gave each group a rocket. One group got the Sky Writer while the other got the Alpha III. While running this little work shop a couple of things were obvious, even adults can't follow simple directions. Over the course of about 2 hrs. we managed to get two rockets built. The hardest part was getting the Shock Cord installed and doing the launch lug. Everything else went pretty smoothly.
The take away from that little trial run was this, Preinstall in the launch lug and shock cord. Build the parachutes and loop them through fishing clasp so all they kids need to do it clip them on. Rewrite the instructions in kid friendly steps.
I went home and installed 24 launch lugs, built and installed 24 shock cords (replaced the rubber with elastic) and typed up some instructions that eliminated the steps I had already performed and repackaged everything up.
Come build day we got there early and setup the work stations. There were two kids to a table. Each table got one hobby knife, one small bottle of Elmer's all purpose glue, one tube of orange model glue, 2 small pieces sand paper and some paper towels. We let the kids come up and pick their rockets. Interestingly the Alpha was the first to go. All of the remaining 10 were gone and only 6 Sky Writers were taken.
I then stood in the front of the room and walked through the assembly of both rockets one step at a time. We did the Alpha motor mount, then the Sky Writer, Inserted the Alpha Fin unit then the Sky Writer etc. etc. until both were built. We managed to get them done in a little more than 2 hrs. No major issues and no one had to go to the hospital
Again....stick to ONE DAMN ROCKET.....!
The following week we spent the first 30 mins letting the kids decorate the rockets, When they were done they brought the rockets up to the the table where we packed the wadding and chute. I then inserted the motor and ignitor and set them aside for the launch. The rockets stayed with me once the motors were installed.
Since the yard was pretty small I bought a bunch of 1/2A6-2 motors and and some C11-3's for the Maxi. We elevated the launch pad so that the rod was well above the kids eye line. This kept us from worrying about someone putting an eye out and made it easier to teach them how to hook up the leads.
One at a time in completely random order we selected the rocket and called the kid to the launch pad. They slide the rocket on the rod, hooked up the leads and walked back to the controller. I held the controller and allowed them to insert the key, count down and push the button. Looking back, I should have mounted the controller to a table or something so that it couldn't move.
We ran well past our cutoff time but we got everyone in the air including the maxi Alpha. Everyone flew and we only had one come apart due to a lack of glue on the fin can. No one lost a rocket but one did land in a tall bush but we go it back. I don't think we were getting them up much past 150ft.