At this time, I do not think it will work with the MESH Plug-in. I believe that the button can only be paired by Bluetooth with a single camera.
Are you saving the video to file or are you live streaming the THETA V?
For streaming, have you seen this article?
Can you share more information on your project requirements so that we can try and answer your question.
For example, do you need to press a button and start a live stream on two THETA Vs or do you need to press a button and then save the video to internal storage?
If it’s a live stream, do you need to stream over USB cable? Or, is Wi-Fi streaming acceptable?