Don't worry mate they won't hit the pistons. You can turn them as much as you need and i always turn them clockwise which is the way they turn when engine is running otherwise you might work the bolts on the sprockets loose. They will jump when turning because of the springs, again this is nothing to worry about.
Well I just had a go at moving one of the camshafts and it jumped which worried me a bit because when it stopped I thought it might have hit the piston, hence the reason for stopping. I am flustered at the mo, thought I had bent the valves?
To turn the camshafts put a spanner on the sprocket bolt and turn as necessary. Doesn't matter if you need to turn back a little, just ensure they are torqued up afterwards.
There is no way you can hit the pistons as they are halfway down the bores and nowhere near the valves.