bmcgonigle,
Why wouldn't you just use the DHCP from the DC at the remote site for the IP Phones? All you need to do is setup a Voice VLAN and let the DC issue out DHCP to those phones with option 125.
As for QoS over layer 2 it would be 5 or 6 depending on your switch; cisco=5, HP=6. Then for Layer 3 it needs to be 46 or whatever Expedited Forwarding is for your Layer 3; I believe that hex is 128.
Thanks,
TE