Classmate invited me to go out with her friends, feeling unsure and need advice

I’m not sure if I should go to this and would really appreciate some advice.

There’s a girl in my class who’s really nice and one day she invited me to go out with her and her friends on Monday. She said she likes mixing friend groups and wanted me to come along. I said yes at the time because I thought it might be good for me I haven’t really gone out with friends in about 2 years, and I don’t have many close friends right now.

The thing is, this would be my first time properly hanging out with her, and it’s not just her it’s a group of about 6 other people I don’t know (a mix of guys and girls). In class I barely speak at all; I kind of go mute. So the idea of meeting a whole group at once feels really overwhelming.

They’re planning to go to an arcade, which does sound fun but I feel like I’d be stressed the whole time. I’m worried about being awkward and not knowing what to say, and making a bad impression, especially because they apparently already think I’m “cool,” and I don’t want to disappoint them.

They’re more outgoing and party , and I struggle in general with connecting to people. I haven’t had a solid friend group for a few years now, so this kind of situation feels like a lot all at once.

Another girl from school was invited too, and I think I’d feel a bit more comfortable if she was definitely going but I’m not sure if she is.

Right now, I’m having second thoughts and honestly don’t think I’d enjoy it. I'm gutted because I would want them to get to know me more but I just won't enjoy it like that. I feel like I’d just be anxious the whole time rather than having fun. At the same time I don’t want to miss an opportunity or seem rude after already saying yes. If I don't go as well what could I say.