well like was said casually doing things is a great way to get to know each other-same goes for her getting to know him. i mean after a while it may be possible to tell how she feels before the issue of dating is brought up. how does she act towards him? (in this case, it would be ok to get an outside perspective). Start inviting her to smaller events (movies with a few friends, dinner at your house with a couple of peole)-how does she react to that? There is no harm in prolonging the getting to know/friendship stage.
Yeah and plus if you reach a point where you feel your friends but don't want to go any further there's not gonna be as big an issue if your not involving other people. The more people involced the more complicated it is and more potential for trouble. Believe me I know that for a fact. OY!