We do our pumpkin patch pictures here every year and just love it. Parking is $5, admission is free, pumpkins are marked for sale. Bounce houses, mini train, wooden cut-outs - all activities are free. There are also concessions and crafts for sale.
There is pretty much no shade, so consider the heat when you dress the little ones. I recommend bringing wagons or stollers.
Also, there is a competing pumpkin "village" that tries to get you to enter, but it is not affiliated and not nearly as cool. Drive up an entrance or two until you reach the official entrance of the FMPP. (More details on that on their website: http://flowermoundpumpkinpatch.com/)