Depends on what you mean with difficult. You could always start with low lvled dungeons, like the 2nd dungeon where the balanced lvl for the boss is 15. But it goes quicker with the 4th dungeon unless they die -.- It should be rather easy, the problems are the spellcasters. Just clear the room of everything except the monster summoning orbs and then just farm the enemies when they spawn before they even can attack.
The problem is to clear the entire room while keeping the chickens alive, but the best thing to do is to choose a place with only melee mobs at the beginning.