I would be very grateful for your recommendation.
Recommendations for what? An Arduino with an LCD, two LEDs, and two switches are all that is needed at each machine, if the Arduinos are all wired to the PC. All that is needed is for the PC to have 4 USB ports available.
Wireless is a different story. Knowing something about the kinds of machines (home sewing machine, industrial sewing machine, 500A 440VAC forge?) and the distances (10 feet? 100 meters? 1000 miles?) would be needed to make any useful recommendations.