If one of them manages to get petrified for the encounter (and I'm planning on stacking the numbers heavily against that happening) my plan is to give them control of the monster the rest of the group is going to be fighting whilst dealing with all the traps.
Sounds good. I kind of realized my comment didn't apply to your specific situation once I started reading your description of what the encounter was like. Sounds like a fun encounter, have you run it yet?