Tons of info coming your way...you watch & see.
First, have you/wife/or kid ever been to the U.S., specifically the "west"? Is this a "Disney" trip? ie: amusement park type trip or a national park type of vacation?
The first n.p. you get to, you will want to buy a national parks pass(gets you in all the parks for $75).
How much time do you have?
We'll get you pointed in the right direction, more specifics please.