It's a science. You all have to jump at the exact same time (which means you have to determine if you jump on "3" or right after), the person taking the picture has to figure out what kind of delay they are working with on the camera because none of us can really jump high (especially when wearing boots), and you have to resist from falling over in laughter.
In the end, you get a lot of great photos. I hope you enjoy them (at the expense of us looking ridiculous)!
(P.S. I promise more pumpkin patch photos soon!)