Because of the low humidity and generally clear skies, you're going to have a unique opportunity for stargazing. Of course, the folks at the observatory will give a bunch of good information and point you in the right direction. But I'd do at little homework before you go
www.stardate.org to see what the night sky holds for you at the particular time that you're there. Maybe sit down with your youngster and see what major stars and constellations and planets will be visible at the time of your trip.
I remember a nice little hike behind the fort that traverses the hills and looks down on the parade grounds and outbuildings.
Hope you enjoy your trip.