A quick note
If you were on Mars looking at Jupiter right now, Jupiter and it's moons (the moons lined up at their widest distance from Jupiter) would be very close to 0.5 degrees (the Moons apparent diameter)
Mars is currently in between its closet and farthest points from Jupiter. I would imagine that at its closest approach to Jupiter, the distance from say Ganymede on the far left and Callisto on the far right, would be around the same apparent width of the full Moon.