well, i'm not the youngest and i had the possibility to be on the flight deck of an LH 737 just some weeks ago (incl. landing).
It was a great experience and made me happy like a child (my last visit was on a DE 727 in 1972 !!!).
So, first of all, you adults out there be not ashamed of asking for a visit -
and to all pilots:
If the workload isn't too heavy, give the interested people the opportunity to visit you on the flight deck and trust the cabin crew "sorting out" potential air rage candidates ....
there is nearly nothing that compares to the view from the flight deck during approach and landing! It's worth asking .....