A wireless/ethernet router as access point, a personal proxy server, or pihole, between your devices and theirs.
Or, if possible your own modem and router.
[ISP modem/router]<--LAN-->[personal wifi router]<wifi>[cheap pc proxy @ 192.168.x.x]<wifi>[all your devices]
Proxy could be ssh(socks5), tor, shadowsocks (not microsocks), dnscrypt, tinyproxy, nekobox, whatever. They'd all have the same internal address from the proxy (if set up that way) and then again one address from the router to their device. (Router and proxy order could be reversed : or just router for some basic device identity privacy - it doesn't encrypt your data though. An encrypted proxy will. And tor or a VPN will mask your external ip)
Some proxies/VPN are more secure than others.
And,RTFM.
A bad configuration can be worse than no configuration.