Lucky you, I say!
The chance to get you hands on an MFH kit without forking out the 200$+ to get one?
I'd be honest with him about the difficulty of the kit, your own level of experience, show him your built kits and say you'd like to try. The chances are it's either just going to sit a cupboard somewhere or his son's going to bodge it up anyway. Personally, I think you'd do a good job on it and would love to see your build thread here.
Alternatively, I'll buy it off him for 100$
j/k