Remember. He already likes you so no need to try dress like someone else , be you. Wear what feels like you. What makes you feel beautiful and comfortable most of all. You're beautiful as you are and he knows that too.
The fashion requirements of Olive Garden and McDonald’s are not significantly different they are both chain restaurants they are both casual dining dress like you go to work. Unless you want to make some kind of impression, then it’s time to think about fashion
Wear something nice like a dress but don't try to over do it, olive garden is casual wear something comfortable but whatever it is don't wear what Queendragonfly suggested that's just a horrible look.
Nope... Don't date co-workers - if it goes bad, you still need to work with them.
SW-User
I think it just depends on your style and your figure. No need to dress to the nines but make sure that you're comfortable and highlight whatever you believe are your best features to help keep your confidence up. It's all going to be about body language and your comfort levels with each other anyway. Have a great time and he'll have a great time. Fun is contagious.
Asking a co-worker on a date? Big risk in that these days. If he asks someone who's not interested, he could find himself quickly summoned to HR and given a half hour to clear out his desk and head out the door. MeToo has reduced if not flat-out eliminated opportunities for co-workers to pursue romantic endeavors.
He's probably keeping things low-pressure. Not my style, but makes sense. I'm concerned about the co-worker angle, though--it can be weird if things go sideways, fyi.