Advice needed: how to photograph a group of 40 people at an important conference?

I've been asked to photograph a very important conference. One of the main photos they need is a group shot of 40 people on the day the event starts. The photo will be taken at a resort. It's not very well lit indoors. Outdoors the light is dappled. They will give me the option to choose the spot for the photo.

How do I photograph 40 people together and have everyone well lit?

Please note I own a Canon EOS R, Canon 50mm f.1.2, Canon 24mm f1.4, Canon 24-70mm f.2.8 (older version) and a Godox V1. No external flash equipment (yet).

Please send me your advice. I would love to take this job but fear my equipment won't be sufficient to take a well lit photo of a big group like that. The conference is in June so I'd have to time to get more equipment if needed.