Since I’m a pilot, one method that I have found very effective is for me to just take the child for a short flight during which I say nothing and give the child the opportunity to reflect on his or her behavior.
I don’t know whether it’s the steady vibration from the engines, or just the time away from any distractions such as TV, video games, computer, iPod, etc.
Either way, my kids usually calm down and stop misbehaving after our flight together. I believe that eye to eye contact during these sessions is an important element in achieving the desired results.
I’ve included a photo below of one of my sessions with my son, in case you would like to use the technique.
Should work with grandkids also.