I guess you have also a CARP IP for public routing/failover?
=> use this IP as OpenVPN Server/Client Interface - so you need only one OpenVPN Server on both sides
OpenVPN Server/Client is then automatically only started on the master firewall on each side...
In newest Quagga package there is also a - I think/hope not final - solution to bind /start Quagga only on CARP master ...
EDIT: Here the Post with Failover found: http://forum.pfsense.org/index.php/topic,58776.0.html
(I found this thread search for a solution why my Quagga won't bind on my OpenVPN server side interface