How can I tell if this is a scam?

I'm selling an old laptop on craigslist, and so far have gotten a couple responses on it, but from "prominent businessmen" who want to buy it from me for more money than I've asked for it, and who both want to "send it by UPS to me son who is going to school in Africa". They say they'll give me extra money for the shipping costs to Africa. I've recieved two identical responses like this, and they ask me for my PayPal e-mail to "make payment arrangements". Do these sound like scams? Can they get anything from me just giving them my PayPal email?