How to routing all traffic through GRE Tunnel Cisco

Hello guys,

sorry for my bad English,

I have some questions about one project with cisco.

The questions are: I have 3 sites and i like to make a VPN (center -> brand office -> brand office).

can i connect this 3 sites with 1 router per site and all site goes to internet through center router? Is it impossible??
Or any site should goes to internet through local router?

i like to gain traffic for vpn and internet and i dont want collisions with internet and VPN traffic..

thanks a lot