Not sure that anyone actually monitors this community at all. Almost all of the answers I see here are those where the poster, eventually, finds the answer for himself and posts it...including this one.
To connect to a RAC, you simply specify the SCAN Listener's "host" name. Although this is a virtual host, ORDS has no problem connecting to it and making use of it.
If you have older style RAC configurations, i.e. lacking SCAN listeners, then you can use the TNS Alias version:
Create file with these entries:
Assuming the file you created was named ords_db_properties.txt, you would load this into ORDS with the following command:
java -jar ords.war set-properties d:\ords_db_properties.txt