Jim is also all for sneaking, but sadly he doesn't have any kind of power that could help with that but once in the prison he could easy melt any chains, bars or anything that got in their way. He would also suggest having someone looking out in case guards come, and offer himself for the job since he can't really help much when it comes to subtlety, and having an illusionist and a teleporter on board it'd make sense for them to do the big sneaking job :|a

THAT SAID he will also probably offer himself as some sort of distraction, maybe using the cargo idea to get inside the city then use his flames to boil water, change the temperatures around and scare/distract everyone while others run inside the prison? On that vein I'd be all of Jim getting caught, too.