Can I ask him out? (without embarassing myself!)?

Okay, I take my mom to the doctor twice a months and there is this male nurse there. He is always super nice and friendly to everyone. The last couple of times we were there, while my mom was in the office, we got to talking. Thinking it over, he may have been flirting with me, but I'm clueless when it comes to picking up signals, so I wasn't sure. It's not so much what he says to me, because it's just chat, but the way he looks at me gives me butterflies! Then, on our last visit, he said "have a good weekend" and smaked my butt! I suppose that should've been a definate signal...but I still think that maybe he's just being friendly (really friendly!) My mom says to "go for it"...but I've never asked a guy out before.

So, any advice? I don't think he can ask because I'm sort of a patient. I think he may be waiting for me to ask or at least give him the green light, but if I'm wrong I'd be too mortified to show my face in the office again!

I imagine the conversation would be:
"Smacking my butt was highly inapropriate behaviour. You can apologise- over dinner. When are you picking me up?"