DR solution

I have 2 remote sites and need a build a tunnel in between them, to pass all the user traffic in case one of them goes down. I have ASA 5525x on each site and 4500x. Was planning to build a gre tunnel in between the 4500x and encrypt the traffic using the ASAs. Is this a feasible solution, am I missing anything, or is there a better way to do this. If one site goes down, I need the user traffic to be terminated on the 4500x on the other side, to be routed properly on the internet