The first advice is the best.
Remember, they are not there to judge you, and what ever you may think, they are not adding up impressions of you to compare notes later.
Be polite of course, and ask a few basic questions of the adults - jobs, homes, etc. and keep the conversation nice and light.
You are not there to be the entertainment for the night, so don't feel obliged to keep the witty banter flowing. If everything is going OK, sit back and enjoy yourself.
You'll be fine, promise!