As a side note, be sure to do some research, (if you haven't already), to learning how to work with small groups. There is a ton of information out there on YouTube and such. (Personally, I did a program of documenting my training of my 8 year old for one year on TennisOne.com...which outlined most of the drills and progressions I used to get her to a high level of play in less than a year working only a couple days a week.)
There are countless ways to teach "correct" fundamentals in a way that is both fun and effective/efficient in terms of producing players who have a solid foundation.
However, there are equally countless ways to ruin a kid's chances of reaching their potential by ignorant and limited understanding of how tennis can be taught.
Regardless of what goals these kids, (or your own kid), may have, developing these fundamentals or what I call "Advanced Foundations", is absolute in terms of giving each kid the tools to take tennis to whatever level they might want in the future. If they are taught poorly, you essentially erase this opportunity.
Dave Smith: Author, Tennis Mastery/Coaching Mastery;
Senior Editor, TennisOne; Dunlop Master Professional