devops – Placing nginx in front of VPS instances

I need to host 5+ instances on different VPS’. All these instances will be web servers meaning I need to communicate with them over HTTP. The issue I’m having is that I need to know their IPs. Not something I want to hardcode from where requests are sent from.

For the solution I’m considering placing an nginx reverse proxy in front of these instances. But that raises two issues:

I would need to manually update the nginx configuration every time I add a new instance. Which isn’t a real issue but time consuming.
The client application doesn’t know how nginx is configured. It doesn’t know which routes are used by the instances.

Any suggestions? Is nginx the right tool or should I switch my attention to something else?