I brought my 11yo son and 7yo daughter for a ride through the tunnel yesterday. We had ample lighting (a must, because it is DARK in there), but not ample attire; I insisted they have jackets, but it was even chillier than I expected.  Gloves and warm pants would have helped!  They enjoyed it nonetheless.

The tunnel perennially rains down in a few places, but was otherwise very dry. We easily managed to dodge all the drips and make the round-trip and stay dry.