opinions on the best way to set up OSPF with failover for a district office with 2 remote offices.

we have a main office using OSPF to communicate with the ISP.

We have 2 remote offices that use only RIP with a default gateway with their ISP connection.

we have an alternate mpls connection for emergencies connecting the main office to the remotes. ( should not be in use unless ISP of remote office or main office fails.)

i need to configure a situation where if either remote office loses its ISP connection it will automatically fail over to the main office and vice versa. if the main office ISP connection fails i need that office to fail to one of the remote site. with a preference for one over the other.

we need all network and VOIP connections to work as well.

i know OSPF routes override RIP static routes. so how do i get the remote sites to use the default RIP route and only use the link to the main office if their ISP goes down.

i can do this manually now by unplugging the main office ISP - connecting the mpls failover circuit - manually adding routes.

i need this automated.

open to suggestions. thank you for your time. also very new to routing.