Which trip would you rather do?

On Trip A, drive the scenic Million Dollar Highway through Ouray, Silverton, and Durango.

If you're going to Mt Rushmore, definitely go to Crazy Horse. It's not a National Park or Monument, but it's well worth seeing. Personally, I'd go with trip A, but my mother loved our family road trip when I was a kid to all those places on B, still talks about it 25 years later.

I live here in SD, and here are my comments on trip B.

If you are trying to pick up as many NPS "passport stamps" as possible, Jewel Cave NM is very close (better than Wind Cave IMO), as is the Minuteman Missle NHS which was cooler than I thought it would be. Driving out to Devils Tower isn't a stretch either... you only need half a day at the park, and like MM, it was way cooler than I thought it would be.

I adore the Badlands. Do the Castle Trail if you have time and want to get away from the road pull-off crowd.

Agree with previous comment about seeing Crazy Horse.

Though a state park, Custer State Park's Wildlife Loop is a must if you want to get up close and personal with a bison herd.

We did all of it, plus Wall Drug, in one 6 day trip.

I’ve done both (minus Sand Dunes because I really hate sand) and I might opt for B over A because of Badlands. Wind Cave is also really cool. Rushmore is really just what you expect but it’s cool to see. Make sure to hit and build some time for Wall Drug between Badlands and Hill City, it’s kitschy Americana but it’s worth the trip.

While I haven't been to any of the parks above, I've been to ~23 of 63 of the parks in the US, and from experience, here are some things I'd suggest to consider in your decision-making: How active are you all/what do you plan to do at the parks? Is hiking in the plan, or do you want to visit parks where you can see a lot by car and/or shorter walk? Are you looking for robust visitor centers with lots to do including interactive activities or ranger programs for kids? And, what is your plan for overnight? Will you be camping, or staying in a hotel? Accommodations are harder to come by in/near some parks - if things like a comfy hotel and/or flush toilets at a campground are important to you - just things to think about and compare the differences for each (and perhaps other Redditors will also be able to comment on specifics). Also, campground reservations for most parks these days get snatched up as soon as they open 6 months ahead of time.

Other than those general things to consider, here are some trip-specific things I can offer:

Trip 1- all 3 of these parks are international dark sky parks, which means amazing stargazing and usually ranger-led night programs in summer months (especially if your trip coincides with a new moon!).

Trip 2 - I know plenty of folks who have done some version of this trip, and from what I've heard, you might want to include a visit to Deadwood in SD.

Either way, I think you're in for a great trip. Best of luck in your planning!

Trip A. You don't need that much time for Trip B.

How old are the kids? I found black canyon a little disappointing until I hiked out to the cliff edges and below the rim a little bit. Also, be there at dawn or dusk not mid-day if you can avoid it.

It’s hands down trip A even if only for the experience of seeing your kids sand sled down the dunes. At those ages they are going to enjoy that more than anything else on both lists.

I've actually been to all these places. They are all awesome.

Trip A is my choice.

Trip A - near sandunes check out

UFO Watchtower (719) 378-2296 https://maps.app.goo.gl/JtAeWgxEVcH56zfY9

There is also a alligator farm near it, but I haven't been to it.

I’ve done both. With that amount of time I would pick Trip B since there is far less driving. You can fly into and stay in Rapid City and do day trips to all of those places. Spend time driving/hiking in Wind Cave NP. I saw more wildlife there than anyplace else. Besides the places you mention there is also Jewel Cave NM (better than Wind Cave in my opinion), Spearfish Canyon/Falls, Custer State Park, Minuteman Missile NHS (great Cold War history and tour led by rangers who worked in Minuteman sites in the area), Wall Drug, Deadwood, and even Devil’s Tower NM. If you hike, I highly recommend one of the trails near Black Elk Peak. The presidents’ statues in downtown Rapid City are also cool.

Love mesa verde and wind cave is underrated. Would have to choose trip A. Not a fan of badlands, and Mount Rushmore is cool to look at for about 5 minutes.

Trip B, also if you’re family’s into reptiles and or birds, go to reptile gardens, it’s like 25 minutes from Mount Rushmore