I am going to meet boyfriend's family for the first time. They are having a bbq/ luau. It is being held at his aunt's house. His aunt said that there is nothing I can bring, but I don't want to come empty handed. I want to bring a nice flowering plant or just a plant as a host gift. Does anyone have any good suggestions? I really want to make a good impression.

You should never go to someone's house for dinner empty handed. If you have offered to bring food and she said no then don't bring food. If you know weather or not they drink, then a bottle of wine is nice. If you are not sure then a plant or bouquet of flowers is a good idea.

A bouquet of flowers is always a good idea if you don't know the host's taste in wine, etc. :)

if you know what kind of food they're serving, then you could always do some wine pairing and bring a nice bottle of wine