We've already been to two of these, and I would suggest a different agenda depending on how old/young your kids are:
Devine Farms is great for little kids (under 3). There is a huge barn with ride-on toys, slides and giant bins full of dried corn kernels for kids to play in. The Barrel train ride and hayride are also little-kid appropriate. And there is a snackbar with pumpkin pie, kettle corn and other treats. For slightly older kids (3-5) there is a giant slide and a bouncy house but otherwise probably isn't too exciting.
Leeds Farm is OK but pricey for little kids (2 and under free but parents are $7), but much better for older kids, mainly because of the ziplines. There are also some animals for petting.
One that didn't make the list is Young's Jersey Dairy in Yellow Springs. They do a pumpkin patch every year and have lots of activities including a barrel train, a petting area, kids play area with bouncy house, giant slide, batting cages, mini golf, and a corn maze. We go out here regularly every fall.