How to lock mac keyboard

Hi, I work at a church and we use a program called propresenter for our service video and such. The youth minister I work with has run into the issue of kids using his MacBookPro between services and we were looking for a way to lock the keyboard and trackpad and require a password to unlock them while maintaining our video output. Does anyone know of a program, preferably free, that would address this issue?

Try LockTight. Be sure to get the version appropriate for your version of OS X.
LockTight for Mac OS X Intel | gkoya