I hate to say I put any thought into this, but given the time they had on the farm, I would of been working on welding some angle iron on one of the trucks.
Stick the angle iron out in strategic points, perhaps some cotter pins so you can fold the iron up (for traveling in tight spaces) but then can fold it down and "out". Sharpen that angle iron like a blade, hop in the truck and go looking to dismember some zombies.
Heck, you could have a triangular shape piece on the front bumper to take their legs off and then perpendicular sitting on top of the bed for decapitation. Take the windows out, reinforce that area with metal, and you'd be all set. Kind of like Mad Max meets the zombies. Make sure you have 4 wheel drive, have a good amount of guns and ammo in the vehicle (just in case you get stuck on them) and you'd be all set for a hunting trip.