There are numerous great meeting spots on the Adventure, but the time, interests and purpose make a difference in what I might suggest. How many people? Right when everyone gets onboard or later in the day/evening? Since most people head right for the buffet at the Windjammer/Island Grill when they get onboard the aft (outside) portion of the The Island Grill is good. But, the pool bar on deck 11 is great, if weather permits. The Viking Crown Lounge on Deck 13 is another good spot.