As an older adult now I look back at some of the family vacations we took. I can say I remember thinking as a kid too much car time at times and enjoying the places once we got there but looking back it was worth it for me and glad my parents did it. We saw some amazing places like YNP among many others. It exposed me to many places and cultures or subcultures of America that I otherwise would not have seen or experienced and perhaps to this day not have made it too. I believe those trips helped make me who I am today in some regards. As some have suggested if you break the trip up on the way out and back like the Black Hills and get a rest day or an out of the car day each way you/they should be fine.
In reality if you don't take them to these places who will? Their future lives may not allow it either so yes you/they may need to suck it up a bit but what great things don't come with at least a bit of sacrifice. We aren't all retired, have a lot of vacation/excess time, have excess money etc me included to do it all the best way all the time. I have done it with my kids and now the grand kids are in the vehicle when possible to help them see what is out there when the wife and I go.
I live in the Denver area and it is quite amazing how many people I have met here over the years that have never gone to the mountains here much less camping in them and they are less than an hour away. I cant even imagine being so tied to a city or my direct surroundings to not even want to see or experience what else is out there, what is around the next corner, what is down that road, what would that be like etc.
