Advice for talking heads gig, low light?
 

I'm doing a gig filming talking heads at a party with a interviewer on the mic asking questions throughout the night.
It's a night gig, indoors, party vibe, load of people in low light.
PD 170 with a light on board.
My question is?
Should i film wide open and stop down until zebras are just gone at 100% or 70%
Or this camera likes it at about 4.5f and stop down until zebras are just gone at 100% or 70%.

I'll do testing but maybe someone has had this kind a gig before?
Cheers
Simon

Is there any way you can add some light to the shoot without affecting the mood of the participants?