Different blocking per computer

A common question I suspect - there are a couple of very old posts on here from 6+ years ago so thought I'd ask again.

I support a local charity with a very basic TP-Link based router (offering private Wi-Fi) to which is attached another router offering a public subnet. DHCP on both routers give out the OpenDNS IP addresses but as they both have the same public IP address, get the same blocking applied.

They'd like different blocking to apply to the public and private networks but I know this isn't possible with the basic OpenDNS account.

Do any of the other accounts offer this functionality? I suspect the answer is no as unless the DNS request is uniquely identifiable or able to be authenticated, there is no way the OpenDNS server knows the identity of the requesting device and therefore able to apply different blocking rules.

Best I can can suggest so far is a) turn off blocking entirely on the private subnet by not using OpenDNS servers or b) some hairy PowerShell script that temporarily changes the DNS server and then puts it back after an hour.

Any other suggestions?