There's this girl from my English class that I'd like to ask out tomorrow. All semester I've noticed her glancing my way in class, sometimes she tries to hide it and then sometimes it's pretty obvious, like she's trying to make eye contact. For example, whenever she laughs (which is a lot, because this is a really fun class) she looks over my way.

I've talked to her a couple times, both in a group and 1 on 1. Multiple times she's jumped to answer a question I asked to the people around me. I've walked out of class with her a few times now. She walks very close to me, laughs easily, keeps eye contact, and touches her hair, so that plus the looks my way tell me she's probably interested.

The thing is, Im unsure of how to ask her out, and I really don't want to overthink it so much that I chicken out or it comes out weird. We're getting out of class an hour early tomorrow, so my thoughts were to invite her along to grab some food with me, or just ask for her number.

Ex : Something like "hey, you seem like a fun girl. I'm heading over to "X" to grab a bite, you should come with." VS. "hey, you seem like a fun girl. We should hang out over break sometime, what's your number?"

I know its a stupid thing to overthink but I kinda like this girl and I'd like to go out with her, so I'm just looking for the way that gives me the best possible shot.

TLDR
Should I go for the instant date right after class? Or just tell her we should go out and settle for her number?