Below is the network topology I will be working with. The left just shows that all sites have a single internet connection. The right shows how I would be setting up the VPN tunnels. The main concern for these sites is that if the internet connection to site 1 goes down the other sites will still have access to site 2. This is needed so the phones will continue to work.
Just wanting to get some input on if there is a better way to do this or some pitfalls I should look out for.