Meeting a guy from online

I've tentatively set up a date with this guy I met online. It's at a little diner I know of, so a public place. My mother is crazy over protective, I'm 21 for crying out loud and I know if I mention it she will try to show up or say I can't go or something. I don't want to just go meet him and not tell someone, what should I do? She and I are close &a I can see why she would be worried, he's 30, but this is also my decision.