how to find mac address of all laptops connected to a TP-LINK router?

In the router setup, if you have one device connected, it will show that MAC address. You can record it, then add the 2nd device, record it, etc....

I usually reserve IP addresses for my known devices - 192.168.0.1 - 192.168.0.9 are my network equipment, .10-.19 are printers/scanners, .20-.49 are computers, etc.....you can come up with your own schema....it will allow you to name each connection, and it assigns the IP addresses based on MAC address.