It's tough to be precise when trying to estimate costs in the future over two-thirds of the country, but I have a few rules of thumb that I use to 'guesstimate' travel costs for planning purposes. The first is that a decent two bed room in a relatively low-cost (but not 'economy') motel will run around $60-75 per night. You can sometimes save a bit by booking ahead, but you can always save by knowing what various motels in an area charge and doing some comparison shopping.

Most motels will nowadays provide some sort of complimentary breakfast that will at least get you on the road in the morning even if it's only some fruit, toast, cereal and coffee. Personally, between that and my own eating habits, I only eat a single restaurant meal during the day and that will be off the breakfast or lunch menus which are cheaper than dinners. If you carry a cooler with you, then you can shop at a local supermarket for salad and sandwich makings, and have those for your evening meal and/or a picnic lunch during the day. So food costs can be highly variable, but for planning purposes, count on $20-25/person/day and you'll eventually find yourselves below budget.

If you are going to be visiting more than 4 or so National Parks, get the annual pass ($80) at the first one you come to and that will cover all admissions for a year. Note that it doesn't cover camping or special fees such as tours that charge, but many ranger and/or docent led tours are free. The Fuel Cost Calculator will let you estimate your fuel costs based on the number of miles you plan to drive and the efficiency of your own car. Use $4 as a relatively safe(?) guess for per gallon gas prices this summer.

So, you have some work ahead of you to figure out a cost range for your trip, but those guidelines should give you a pretty accurate idea.

AZBuck