Looking nice Dan! We planned a similar thing with modular control/ESC boxes when we started the Scot-Bots kits but didn't get round to implementing them before they went on sale. We're getting more involved in school things now though so they've moved up the to-do list. It will be good to follow the progress of yours as well.

And best of luck with the summer school club too, that'll keep a lot of kids entertained. Not sure if you're aware of it or not, but if you find yourself needing extra bodies to help run the club, stick a request in for a STEM Ambassador, as the activities would definitely qualify and it's something that a fair few people would be interested in helping out with: http://www.stemnet.org.uk/content/stem-ambassadors