When I visited Jupiter, I had a hard time hitting any moons, and I was doing it on purpose, so I think you're safe.
If you want to do it the realistic way, you should orbit at around the altitude of Callisto, since radiation is low enough for you to survive there. You also have access to a big moon which has a lot of ice (which you can make water out of, and out of water you can extract both oxygen and hydrogen, so you have what to breathe and fuel too. Besides, ice will be handy to shield yourself against any radiation.) Of course, all this doesn't matter in Orbiter, but you might find it fun to simulate a mission you could actually perform IRL.