Given that Thief gets UMD by 13th level and the adventure is scheduled to end with characters at 10/11th level, that's probably not going to cut it.
The Druid will be a Moon druid, I am uncertain about the Rogue 'cause it's going to be her first time ever playing rpg's (and also my DM's first time DM'ing 5th). I don't want to rain on the Rogues parade and tell her what to do and don't too bluntly, but I find myself slightly bothered by the fact that my second idea of playing a Light domain Cleric will mess with her light sensitivity a lot*. Oh well, I have about a week to figure it out... let's get back to the drawing board and consider my options.
EDIT:
*Not to mention the Dawnblade/Sunblade or whatever it's called... I... should probably mention that part to my DM and the Rogue actually... if she's going to be using it and fight constant disadvantage, that's going to be terrible. Like... real bad.