What to pack for my up coming trip?

I am a junior. I still wear briefs. I have to go on a summer retreat trip for my church. Their is mostly preps in it. I have to room with somebody. I don't have any boxers. Does it matter if i pack briefs? What do most guys wear? I can't stand boxers. I wear the hanes and fruit of the loom briefs. Are they the tighty whitey kind? Will i be made fun of if they figure out. I am not very popular at church. I normally sleep in my underwear also. Would they say anything about it? Past trips they slept in their boxers.