I would use a basic QoS design to identify the traffic of interest and also route that traffic through your VPN tunnels. Set it up once right and then you don't need to revisit it later.
What I typically recommend is to allocate 33% to RTP and 5-10% to C&C depending on the bandwidth available. everything else is best effort.
Are you going to be doing video as well? that would also go into the 33%.
hope this helps,
-t