One thing about the Florida Keys, from December thru March the Campgrounds are mostly booked solid with 'snowbirds' from the northern states. The CG owners boost what they charge a lot, $100/night US for example. That's the 'season' down there. Off season the prices are much more reasonable $40/night maybe or less if you book a longer period. The crowds are diminished but a lot of restaurants and such may close, but there are plenty of businesses left open. So planning to get to the Keys during that off season is a good idea.
There are many diving boats which will take you out to the reefs and provide you with snorkeling equip (and a lesson if you need it). The reefs are spectacular. These trips are fairly cheap, maybe $30 or so and well worth it. They also take SCUBA divers out incase you do that.
Assuming you want to see the major National Parks, I would plan a route thru Glacier NP (Montana), Yellowstone & Grand Tetons (mostly in Wyoming), down to Utah and Arches NP, Capitol Reef, Bryce Canyon, Zion and the North Rim of the Grand Canyon (Arizona. You can divert to Mesa Verde NP in Colorado.
That is just the major parks there are scores of other parks and attractions along that path. Rocky Mountains NP is in eastern Colorado. But I assume you been to Banff the the Icefield Pkwy so that sort of scenery you are familiar with. Great Sand Dunes NP is someplace different and it is in south eastern Colorado.
After that you will be out of major parks until you get to Great Smokey Mountains NP in Tennessee. But they are having a lot of wildfires right now and may not look their best for a year or two. The Everglades NP is down just above the Keys.
