I agree with Mrs.O.
We have been on a couple of these and don't think they would be suitable for ages 13~15.
Any kids would either be bored,or some might even be scared.
Usually not much happens for some time,and then all hell breaks loose.. Neither of which would be suitable for age group you mention.
However,as Mrs O says I think this is all academic, as I believe participants must be over 18.
I have just trawled through several of the Murder Mystery Websites,and they all seem so say 18 as a lower limit.However,most say that 12 is the youngest that can attend(that is stay in the hotel etc),BUT they will not be allowed to actually participate,which I would think would be most frustrating!