Well after almost 25 years teaching youth, I find I only use traditional karate training. Addressing their attention spans Classes are only 1 hour long, and we normally change drills or activity about every 7 to 8 minutes.
Maybe once or twice a year we play some games, but that is not a regular occurance in our classes.
One way we keep the students minds involved is every class is structured differently from previous classes. We never follow the same order of instruction. This keeps their focus on the drills we are using. They never know what will be coming next.
We also practice with all ranks together. This inspires the junior students working with those who have passed their level previously, and for the seniors to remember how far they've come.
With this approach, however, different kyu may be using different techniques at the same time. For example the White belt may be working on front kicks, the Green belt may be working a front front kick round house combination and the Brown Belt may be working a double round house combination all at the same time.
Likewise for kata, we break them into appropriate kata groupings for instruction.
The reason I don't use games during training is simply I'm teaching karate, just as I would with my adults, and I'm loathe to have them spend time in activities which do not work to increase their skills.
Such is my vision of Youth Karate.
Bushi No Te Isshinryu www.funkydragon.com/bushi