There's a bus that runs from the airport to a regional bus station at RTP, which connects to a bus that takes you to downtown Raleigh, at which point you can get on a Raleigh city bus to wherever in Raleigh you want to go.
Instead of all that, I imagine that somebody could just pick them up. If not you, somebody with a car. If there's someone that goes through the effort of flying in to play, I think the least we could do is get them from the airport.