I have never been to a large multi-day gathering like this. Aside from Saturday dinner, are there planned group rides/events? Or is it all concocted ad-hoc in the lobby of the lodge? Perhaps just FJRs randomly buzzing the country side.
Show up, meet a new friend or two, go for a ride... there will be lots of different groups going different directions at different paces... just depends on what you want to do... many will be arriving on Thursday. My personal plan is to head into the park on Friday to see the waterfalls and out to Glacier Point... I've been many times but it still leaves me gobsmacked... Saturday will be a day ride in the area TBD... there is lots to choose from!
That being said, since you're new to the group and all the personalities, please make sure you don't get in over your head by pushing yourself beyond your limits... that never ends well. Not a put down at all but given you are the only one who knows what pace your comfortable with, just be true to yourself. SOP is the leader of the group will wait at turns for everyone to group back up before proceeding so no one gets lost or left behind... Now
THAT being said, know where you are and how to get back to the hotel because even the best leaders have left a rider behind inadvertently... cough, cough.