Best way to determine all nodes in a mesh network?

I am using XBee Pro Module - ZB Series 2 in API mode and for my application the number of routers and endpoints will change from use to use. It is my understanding that the coordinator finds all member nodes at initialization and then will periodically recheck. Can I access this list of members that the coordinator recognizes or do I need to broadcast an AT node discovery command to the entire network and then tally up a list of responding nodes? Ideally, I just want the NI parameter as I’ll be using it to describe system functionality associated with a particular node.

I think you have that a little backwards. The Coordinator establish a network. Then the routers and end devices join the coordinator. The only list that the coordinator keep track of is the end device list. That list can be queried using a ZDO command (Child table).

The other is best used by issuing a Node Discovery.