Overall the experiment was only partially successful.
While the concept worked with using the Bluetooth transmitter to get a signal to the wireless headphones, the delay was too extreme to overcome in last nights test.
I think this was a lot in part to the particular venue and the volume of the players. Since the room was so live, and the drummer so fierce (my nice way of saying too loud) I had only vox and some guitar thru the FOH. For the most part drums, bass and a lot of the guitar needed no reinforcement from the system and the faders were off. When listening thru phones, the slight delay on vox just didn't mesh with what I had to hear coming off the stage
In our usual outdoor and large club venues when everything comes thru the mains the delay may not be as bad givin that I would hear everything with the same delay.
Purpose was not to "mix" with phones but to be able to block the overall volume and still be able to make some tweaks if needed to individual instruments.
Will retry at a larger venue and will still try the regular, standard, non- Bluetooth wireless phones and try bump the volume up a bit.