vcenter and 2 different geographic sites

Hi Group.

We are proposing adding a DR site.

Today we run vsphere 5 enterprise on 4 servers with vcenter standard edition.

For our proposed backup site, we want to purchase 3 vsphere servers and replicate to them  using veeam as we have already paid for it.

My quesiton is this.  Do we need to purchase another vcenter server license for the backup site or can we simply incorporate these 3 new remote vsphere servers into our existing vcenter under a different datacenter and cluster?

There is a chance we might like to run a few vm's off by themselves at the second site as well as the replicated vm's.

Thanks for your advice.