It's good to have travel books when you go to faraway places. However, what you'll probably use even more over time are books about places to visit within a day's drive of where you live.
This is probably more important once you have kids. I would think you'd want to leave less up to chance and know where you're going and what to expect when you get there. Plus, shorter car trips are a great way to start preparing them for more extensive travel in the future.
One book with a lot of information for seeing Arizona is Day Trips from Phoenix, Tucson and Flagstaff by Pam Hait. There are lots of suggestions for trips you can take - with accompanying maps. The destinations include lesser-known sites as well as the big attractions.
Because it's so packed with useful stuff, we overlook its counter-intuitive organizational structure (i.e. there's more than one "Day Trip 01" and no index). It's worth the extra page flipping.