hey! I was reading The Monster under the Tower and a lot of questions showed up in my mind from the intention of the adventure.
the statblock given to the mage is that of an Archimage (a level 10 wizard), which seems quite strong for level 2 characters, and could easily kill the two werewolves.
how are the players supposed to beat the mage if they wanna save the child? or if the players are supposed to be the meat being sent down there to feed the beast? did your players manage to beat him when you tested the adventure? seems like they'd go out with at least one dead (if not all, from a fireball)