The gateway router would be the simplest point to setup QoS. What router are you using? Any other pertinent info about your network would be dandy, like important devices like the routers, switches, AP's.
A cheap and powerful way to get state-of-the-art QoS is to load up a PC with a Linux-based firewall/router Operating System like IPFire, which will replace your current router.
There are many different ways to accomplish your goals. Just a few quick scenerios:
Limit everyone to a ~11Mbit (perhaps schedule the limit to disable during work hours), and allow your devices all unused throughput, meaning you will get a minimum of 3Mbit.
Split throughput proportionally among everyone or perhaps every device. This can be setup to dynamically allocate depending on the number of devices.
You could specifically limit the max throughput of each individual traffic flow originating from Netflix.
Some methods will have minimal fluctation of worst-case latency but you would need to sacrifice a little bandwidth. Or you can prefer max bandwidth and accept large fluctuations in worst-case latency. Or you could choose a finely tuned, overly complex QoS setup that adapts poorly and requires lits of maintenance. Or maybe a setup that is simple, adaptable, but wastes a little bandwidth.
I think you can even sign into your Netflix account and put a limit on the video's bitrate/quality, perhaps disabling 720p and higher.
Lots of possibilities and lots of trial and error. Knowing your router's capabilities is the first step.