PS is quite good for scoring matches. We've been using it for the last 4 or 5 matches and it's been mostly trouble free. Once the match starts, syncing regularly is important. We use a combination of ipads and galaxy tabs, mainly as I have an ipad with cell service that can pull down the match and be on-line if needed. It also acts as a wifi hot spot for the sync network.
Would suggest you run a coiuple of practise matches before a real one to get up to speed on some of the more involved things. Things like adding new shooters, changing squads, recording the score on the wrong shooter, some of these can cause grief if not done right.
Read the PS notes, they are quite helpful. For the first match or 2 maybe have a simple paper score sheet to use as a backup, just in case. Make sure you have lots of large zip lock baggies in case it rains. Make sure you have a charging source, as iPads will run low on battery if running them all day. It's kinda nice the way you can define the match and stages on the ipsc website, then dld the match to PS. Upload is pretty easy too.
Mostly, take your time and practise before you have to score the first match.