Just a thought burlap bags are cheap and this combo with ribbon would probably look better than the cheaper chair rentals. Would do a navy ribbon with bow (no flower or wheat stalks if we wanted), then table runner would be navy as well
Seat cover for dining chair. Clean, simple wrap around design that fits snugly around legs with velcro. This would be simple to make by altering this DIY: http://www.athomeonthebay.com/2012/03/dining-chair-drop-cloth-slipcovers.html
Quick and easy folding chair covers...Dollar Store rectangular plastic table cloths cut in half, drape over the top and tuck the other end through the opening in the chair. Fluff and anchor with napkin ring.