I'm not a very good gamer, but I've started a new game at master difficulty with a mod that allows you to have more than one follower, because I wanted to try playing skyrim a bit like dungeons and dragons (roleplaying an adventuring party). Do you know any dungeons that wouldn't kill my little "three-person-army" directly? How do I get to it/them?

Is Bleak Falls Barrow too hard? I personally like it a lot, and a quest is involved. Seems like almost perfect dungeon to me, and it's not so hard.

You'll just have a problem with the bad pathfinding (ergo your followers getting stuck literally everywhere, especially in small corridors), and your followers setting off all traps again ... and again ... and again ... and again ... and ...

The latter can be solved with a mod 'though, and for the first one you'll have to be even more watchful over them than a mother hen over her chicks. And even then it can get quite frustrating (watch GophersVids' playthrough on youtube if you want to get a good laugh out of it instead. It's a wonder the poor guy didn't get a heart attack).