I'm writing this from a non hobby point of view, and purely from a joy of travel POV.
Within the US, for natural beauty there is no place like Glacier National Park, especially if you enjoy back country hiking. Even the day hikes there though, are not over crowded. I just love it. Keep in mind that the season is fairly short because of snow fall. late July and August are best if you want a back country experience where the high passes aren't snow covered. The Going to the sun road is generally only passable late June through late September.
A close second is Yellowstone, with its magnificent geological formations. It can get a bit crowded in the summer for my tastes though, and I recommend spring before the kids get out of school.
For coastal beauty, I generally prefer warm water, but that is hard to find in the US with a location I also love. I lived in Mexico for several years though, so if you want some suggestions there, I can help. For the US, if you don't mind cold water, then the coast of Maine is quite gorgeous and wild, and makes a lovely summer road trip (I'll fly up, rent a car, and just spend some time driving up the coast). The same goes for the PNW also.
For cities, I absolutely love Chicago! I've lived all over, but keep coming back here. The art, the music, the food, and the lake front! It really is fantastic. And if you don't mind a suggestion just north of boarder, Montreal is another favorite. It has similar offerings to Chicago, but smaller and with a French accent.
Have fun!!