The Need for a MAC Address Inventory

I need to inventory the WiFi MAC addresses of all our devices. This not only includes our tablets, phones, and laptops, but also our routers. I just realized then that maintaining these devices is tedious work. It's like I'm the sysad of a small network but now I even have to perform these tasks at home, taking up my free time. I have to take the inventory because it was taking hours for my wife to download her daily work files using our home broadband connections. 

When we use instead mobile broadband connections, what would take hours would now finish in a couple of minutes to half an hour. What my wife noticed was that the slow download speeds would occur starting at 7 PM in the evening. This could be due to any of a number of factors, including overall congestion of the network, but just to make sure, I decided to block any unknown MAC address from connecting to our routers. It could be better to allow only known MAC addresses to connect but I have to weigh both options later.