lizzybaxter, not unless you're prepared to spend an hour or more a day training them - and doing this for a while. Guineas are still "wild" with all of their wild instincts intact, and it's tough to overcome them. It's been done, but rarely, and with a lot of difficulty. You CAN, however, get them to trust you to the point where a) they don't freak out when you're around and b) will take treats from your hands.
That's not too hard to do, and just requires that you spend a lot of time around them, very very still, and giving them their favorite treat from your hand. It took me about two weeks to accomplish that with mine. They'll come up and peck my jeans, shoes....but if I reach out to touch them, they dart away. They do freak out if I try to catch them though. That's best done at night when they're on their perch/roost. LOL.
I say, and this is only my opinion, get your "lap bird" needs met by your chickens and let guineas be guineas. You'll be crazy about them whether you can pet them or not anyway. They grow on ya.