Why not have everyone wear Western wear or even square-dancing costumes? Could you invite guys, too, and hire a square-dance caller and someone to teach y'all in your spacious backyard? How about line dancing? Or do you just want to play Garth Brooks on the CD player and have the guests wear their boots? You'd probably serve a red-meat barbecue—no tofu for this crowd! Or maybe chili, and you could send everyone home with a little package of chili mix.
You could provide everyone with a neckerchief in bright colors—many hobby stores carry them for as little as ninety-nine cents each. You could use a few bales of hay for seating in your backyard.
For clever invitations, buy some brown construction paper, some small chicken feathers (or pull them from a pillow), and a small square of fake leather, leopard skin, or calico fabric. Cut the construction paper into little hat shapes, leaving the top of the hat with a seam so that it opens like a card. Cut the fabric into tiny strips to make hatbands and glue the feathers into the hatband. On the inside, insert the actual wording of the invitation. Yee-haw!