It is not okay to register someone else's IP address with your account. I.e. do not run an Updater outside your home network.
But it's ok to configure OpenDNS resolver addresses on your roaming device, the normal ones or the FamilyShield ones, to try using OpenDNS. However, if the network admins of that WiFi don't allow for using 3rd party DNS services, it simply will not work. You'll have to find it out.