Advice?

I was asked to be a date for a wedding and I agreed. However, he just texted me he has something to tell me in person at the wedding and I’m nervous he’s going to as me to be his gf. I’m nervous bc I don’t want to be put on the spot like that. And I really don’t know this guy to well. I’m scared his family is also going to ask if we are dating. I’m really just nervous in general for the night. I don’t know how to dance… and I’m just nervous to meet his family. I’m nervous I’ll be over/underdressed. But besides the nerves I’m just excited to hang out with him and have fun.