Bobo -- "A Bit Shy at First, but then an Extrovert."
"Hi there! Listen, I'd love to head out to the crag with you and climb, but I wouldn't mind just watching you climb, either. Hey, I'm Bobo by the way!"
Bobo's slight lack of enthusiasm has nothing to do with being scared of heights. He just feels helpless hanging from your harness, should you take a fall. It's probably best you let him get some climbs in himself to get comfortable.