You will get experienced people using their own gear and know the do's and dont's, in a way this will make your day easier, however, they will tend to push the bounderies a bit more, i.e. wipe/loose hits.
If you see someone being rained down on, then get close and watch and wait because they are likely to get shot, dont be afraid of being hit, its part of the job.
A good ref will get stuck in, especially on walk ons, because these guys take it alot more seriously than normal rec punters and probably the worst thing to happen for a walk on player is people constantly and blatently cheating.
Also, preventing this stops alot of over shooting, since cheating is one of the main causes of over shooting, but main thing is, enjoy the day, if you are enjoying it then generally so is the customer (mostly) and this is the desired end product.