Your first ponit is rigth, you need to separate each Point to Poin link between routers in one subnet, like you said:
Always taken one IP for the centra router and other for the edges routers.
The problem with one subnet is WRONG because one subnet if for SWITCHES, not for routers, routers DIVIDE broadcast segments, and one subnet is that, one boradcast segment. Every port of the router must be located on a different subnet, on the way to ROUTE traffic form one to other.
I think, this one could be a rela scenario, remember that major clients connect to it ISP accross a DSL, a modem-router, and then, the ISP, seeing like your central router, ROUTE the traffic from and to internet.
If you are plannig this scenario to some enterprise, or something like that, you can less behind the 5 edge routers on your scheme, and only use the central router. With that, you can save money of that 5 2811 routers, and also your network will work FINE.
Also, you can configure a DHCP server, to provide the addressing oon every subnet (every port), saving if you like, the first or the last one IP address of that subnet to your router port.