Hey All I am very new to this site and to audio field work in general>

I have been tasked to improve the quality of or recordings in the field, well the audio part of it anyways. I am looking for whatever help/ideas you can give me in order to improve the sound quality of our round table discussions. These discussions normally take the form of doctors sitting in a "U" formation with our host at the head of the arrangement. The host directs comments and questions towards all of the panelists which means he tends to turn his head left and right. The panelists do this as well but less so.
We need to ensure the best sound pick up for all of the participants but in particular the host. As well to complicate matters we will be renting wireless mics (my boss does not want to see microphone cables on the video). We have tried over the ear systems (the kind that ends up sitting to the side of the mouth kind of like a boom mic). Our host hates the and they usually end up coming loose on one or more than one of the panelist.
What microphone system (tie clip etc) and placement do you recommend. I would prefer to go with a lavalier/tie clip set up as our host hates the over the ear and tends to knock those around as he puts his hand up near his mouth a lot.

Any help would be greatly appreciated