Long but leisurely trip from NH to NM up to MT then home

You are probably OK this time of year w/o reservations. The only time we make them during the summer is when we want to stop at a major National Park or during holiday periods.

If we know what type of thing you want to do and see it would be easier to make recommendations.

You will probably run into bad weather and you may have a problem finding any open campgrounds in some areas. The higher altitude areas out west may still be snowed in. Bryce for example. And Montana parks.