I have some photos of me and a couple of 4-degree classmates in them ... or not.
If you were going to go into them, I hear that one of the numerous entrances is near the observatory. Big, concrete structures sticking out of the ground with a metal hatch with a ladder that leads down into the tunnels. Have you ever seen a Fallout Shelter sign that says capacity 6000?
I've also heard that they extend very far - all the way from the field house to the hospital. Rumor is that they are extremely cool, including classrooms, dorms, and even a morgue. Essentially the entire Academy - subterranean. Part of the tunnels might actually be in somewhat common use by USAFA operators, e.g. equipment rooms for the mechanicals at Fairchild Hall. Some entrances might actually lead directly to locked doors at Sijan and Vandenberg.
Nowadays, with cheap, easy cameras and remote sensors, I would be very, very cautious of such a prank as going into the tunnels. Times have changed. There was a threat of pretty-stiff punishment back in the late 80s. If you want a preview to what they may look like, take the tunnel from the field house to the gym. That is actually part of the tunnel system that is actually open for use.