VPN solution config help

I want to connect 5 remote routerboards over the internet via VPN (ipsec/l2tp) to a main routerboard in a datacenter, I want all traffic including internet traffic thru VPN, so if the VPN is up, surf the internet thru the datacenter routerboard, and if tunnel is not, surf out the local internet connection, any ideas/wikis to follow?

Thanks.

Here you can find examples how to set up ipsec
http://wiki.mikrotik.com/wiki/Manual:IP/IPsec#Application_Examples