If my router had an option for dynu, I'd use it of course.
Were the router were to go down, then all my servers would be unavailble.

Clearly, I need to use your Updater software, but if that host fails, my other servers would still be up, but unconnectable if the dynamic ip changed.

Is there a way of installing the Updater software on all my servers, and have some diversity or round-robin feature, so that connectivity for any server to update the IP, thus ensuring other servers were always available (different ports of course)

Thanks

Are all or some of your servers located on the same network? If so, running multiple instances of the IP update client would definitely create some redundancy.