Newbie Routing question and IP Addressing

Hi, I have the job to setup about 4 Canopy networks in 4 different citys.
Each of the citys would probably have about 200 subscriber modules.
To cut down on the management overheads and costs I would like to be able to just have the Bam servers in cityA and have all the AP’s authenticate to the Bam servers in CityA.
To do this I guess there are two methods I can think of.
One - to setup routers at each city connected to the main internet feed and to have them create VPN Tunnels to CityA so all the citys can route through to CityA.
Two - to have the ISP create links between the citys for me but this would be more expensive.
Also any Suggestions on IP setup would help ie: what ip address ranges to use and how to seperate the IP networks of each city.
Also Suggestions on the type and make of routers would help.

Any help would be appreciated.