We had "One Voice" at the invitation only last night of Rush. For us, COB was a one night only party after formal rush bids were distributed. Is that the same for you and your colony? At COB, we had a regular rush party with food and songs and getting acquainted. We incorporated "One Voice" and the wishing well at the end of the party. The Delta Diamonds were usually newer sisters in charge of making sure that we had all the important information about the rushees.
Oh here's another rush theme that worked. We had a big jigsaw puzzle of a unicorn. Every rushee was given a piece of the puzzle which had the name of a sister on the back. The sister and rushee had to find each other and put the pieces of the puzzle back together.
To everyone - Good luck with your rush parties.
I hope that these posts contributed to a successful rush!