Too much for a BBQ/anniversary party where I'll meet my boyfriend's extended family?

So I was invited to an anniversary BBQ for my boyfriends grandparents and I'll be meet extended and overseas family for the first time.

I recently gained weight and don't have a lot that fits. This is the one dress I have... Is it too much for a BBQ? I know it doesn't do anything for me but I at least feel cute, but wondering if it's too much and I should look for something else?

My hair would be styled up in a sort of French twist or a blow out with a off white textured sandal.