What should i wear..???plzz help 15f?

me and my boyfriend have been going out for a year i have already met his paretns and brother just not his grandparents and unlces. his grandparents are about 55 and his uncles are 22 and 21 also they are brining there gf i am soo nervous because we are going over for new years dinner they are all candadian french soo what should i wear please please please help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!…