Milan for an 11 year old German speaking boy

Hi
beginning of April my 11 year old cousin will come to visit me in Milan for four days and I am wondering about things to do with him. As he is German he doesn't speak Italian, which rules out quite a lot of ideas I first had.
Unfortunately I do not have any friends in Milan with children at this age, hence this thread. Anyone any ideas on activities (besides watching soccer obviously :-))
Thanks
Jana