Would it be possible to live on a gas giant moon?

I have an odd fascination for wondering what exotic living locations would be like, such as a Dyson sphere. After some thinking today I wondered if anyone knew if it would be possible to live on a moon of Jupiter or Saturn, like Titan or Ganymede, if the following assumptions were true:

1) There’s a breathable atmosphere
2) The moon has an atmosphere and magnetosphere (or whatever) that solves the problem of radiation

For instance, many years in the future the sun expands until it’s close enough (or hot enough) to warm the moon in question enough to allow life (we’ll go with ‘life as we know it’). Let’s say it’s Ganymede, which has a magnetosphere, it warms up, spews some water onto the surface and manages to hold on to an atmosphere.

Would it be livable? Or would the gravitational forces between Jupiter, other moons, and the sun (at this point in the future) cause too many surface instabilities? Given the size of Jupiter, would its journey around the mother planet and Jupiter’s trip around the sun cause problems? Like being in the dark too long?

Do we have any astrophysicists around?