What kind of router is it? There are some other things you may be able to do like conditional static routes.
I think OSPF is an ok option, but if a single AP happens to fall to a backup controller for some reason, that controller will start advertising that AP group's VLAN subnet and your downstream router will have two equal cost routes and you will end up blackholing traffic.
Like Colin said, in a large campus deployment like you have, using the downstream router as the L3 gateway is your better option.
As far as router redundancy protocols, you can use whatever your router supports. VRRP, HSRP, GLBP, etc.
Keep in mind, you're going to have to change your controller and router (switch) ethernet ports from access ports to .1q trunk ports as well to carry all those VLANs.