I did it twice on commercial airline flights and once on a military C-141 at Newark airport! The crew was more than happy to let me sit and chat with me about the aircraft, as well as take pictures!
The C-141 was there with President Clinton. They carried his limo and the secret service vehicles. I was an airport electrician and my co-worker and I had to setup portable lights around the aircraft before dark.
When we were done, I asked the crew if I could see the cockpit. This was years before I got my PPL. They were very welcoming and took time to explain the systems as well as take a picture of me in the Captain's seat!
So you're probably in NJ by now but on your return flight, ask the stewardess just after landing. Let everyone else rush to get off first....that's what I did
Please don't be afraid to ask, the worst that could happen is they'd say ...unable.
Oh yeah, congrats on your flight and enjoy your sister's graduation in this heat! I'll be at my daughter's graduation in Montclair, NJ tomorrow....it's going to be outdoors! 90degree heat