What WiFi nodes are you using and how fast is the router?
If the nodes/switch/router are 1Gb Ethernet I don’t think that would be the contention. (Jumbo packets would help there, too, as you can transmit data in fewer packets.) if they’re somehow on 100mb Ethernet that’s your bottleneck.
WiFi also depends on what you’re using. If you’re using a typical 2.4/5g band WiFi especially 802.11ac or higher I’d think that’d be enough to handle 5 people gracefully. I’d google for optimal advanced wifi settings for your router, too. Some of the default settings will slow things down for max compatibility and you might have QoS turned on (or you might want to turn it on)
Again, my bottleneck went away when I replaced my Ethernet hub with an Ethernet bridge. I didn't expect much improvement but it worked great.
My expectations were based on my belief that there would be less packet collisions with all child nodes talking only to and from the parent node. Basically the parent node is always part of the communication, and each child node respond when it's receiving the packet (with mostly download info from the internet, though there is some upload from child nodes to parent node). So I expected practically no improvement from adding the bridge. But it was cheap anyway so I tried it and it's worked great for about 5 years.