Going with relays is one option, though the wiring can be tricky and if one relay fails the whole system goes down.

It would be easier to use a normal bi-direction ESC for RC cars.

Some examples are the Botbitz TZ85A ESC, Electronize FR30HX and Victor 883. However these are very high ampage and high voltage so you just need to find something a little less over powered.

Though if it was me I would used a TZ85A as it would last pretty much forever and you would never have to worry about breaking it.