Oracle RAC Failover functionality clarification
Just from Oracle side there is nothing to worry about. You could even do this operation during normal business hours.

BUT! most Applications are not cluster ready. They cannot deal with this situation and will crash. All services are still available since they are migrated to the second node. But the session does not get migrated that's why the client will loose the connection. An application which supports RAC would then reopen the connection and just continue to work. 

I would plan a downtime for this operation.

For the future you could bond two network ports for the public interface in failover mode. With that setup you could do the operation without downtime. Note that bonding in load balance mode does not work so well -- at least this is my experience.