Sounds like you have a basic design plan already. One critical element is the circuit provider who can service all of your locations. You need a telecom partner(s) that can meet your uptime requirements and offer pricing at the level appropriate to the service(s) you require. Are you managing this yourself? If you don’t have any Cisco or VPN expertise, then this could be a large challenge to handle. Some telecom providers like ATT or Sprint can help with management. Alternative management solutions would include virtual network operators like Virtela. Their network uses multiple providers across the backbone so an outage in one provider’s network does not take down the customer’s networks. However, remember the “last mile” is always the most fragile and susceptible to problems. I have had good experience with Virtela across a multi-site, multi-national network. I don’t have to worry about the daily management of the routers, circuits and performance issues.
Good luck and feel free to ask for additional information from your provider. Don’t be afraid.