I love fall fests and pumpkin patches, so we have been to MANY in the past 5 years that I have lived here. There is one that is just above all the others by far, and that is Stade's Farm and Market.
http://www.shadesofautumn.net/home.php
They have HUGE HUGE fields of pumpkins that you ride on a hayride to (pulled by tractor) and gather them yourself, then hop back on and ride to the market.
When you pull up, you park in a huge gravel field. The huge market is in front of you decorated with walls of mums and gourds of all varieties, cornstalks, etc. making for GREAT photos. There is a VW bug painted like a pumpkin off to the side. There are some tractors the kids can sit on, hay-bale mazes for the little ones, corn mazes and fields, hot apple cider and donuts in a big open-air barn behind the market (which also sells all kinds of produce.) There are carts for you to pull your goodies around in, if they are too heavy too.
There are bounce houses, haunted houses (not so scary from the outside if you have toddlers), live music, a pumpkin cannon off in a far field (but visible), a little train (no track), pony rides, etc etc etc.
It's all close together, but spread enough that you don't feel trampled. You aren't walking MILES, and yet spacious, if that makes sense. It doesn't seem overwhelming to the kids like some of the carnival ones do either. It is more just enjoying the fresh air, maybe doing the bounce house and train, getting a donut, taking some pics, riding the hay ride, picking out pumpkins, picking out pumpkins... picking out pumpkins. :)
Hope this helps!