Have done a few major darts events in recent years and, yes, there is a lot of stuff going on amongst the audience you can cover so, yes, a couple of short/standard zooms with a flashgun will cover that. As regards shooting the players in action it's all about shooting from very clearly designated and limited positions that don't get in the way of Sky's cameras. Flash isn't allowed and you can't shoot from stageside during live play. If it's a Matchroom event they have their own guy there who will definitely give you a heads up on what you can and cannot do, especially in the area immediately adjacent to the stage. If he doesn't seek you out you should make every effort to find him so that you don't put your foot in at any point. The further you are from the stage the more freedom you have but you'll always play second fiddle to Sky and the paying punters.