You don't need a managed switch to handle QOS. This is a home environment. He has probably the wifi router and maybe a device plugged into it for the hardwire, or an unmanaged switch. Most modern home routers support QOS to some degree. If you're going to want to traffic shaping you'll want an L3 capable switch but that's way beyond the scope of what he's dealing with.

Just buy a better connection, if you can.