My family will be driving from St. Marys in Glacier NP to Rocky Mountain National Park next summer. I am looking at driving the 8 hours, stopping in Cody for a couple of days before continuing to RMNP. However, I am not looking forward to an 8-9 hour drive, so is there another good place to stop and visit about 4 hours into that drive? It doesn't look like I am driving through any major towns in Montana (roughly 4 hours into the drive), but I am not familiar with MT. We will have a 13 year old and 9 year old with us. We will have already been to Yellowstone, so I wasn't planning on stopping there again.
Thanks for any info!

How about Thermopolis? It's got a beautiful location, a terrific dinosaur center, a park with huge thermal pool and thermal features, nice river paths, and a good selection of lodging. Probably half way to RMNP.

That's tough. There really ins't much between St. Mary's and Cody in the way of breaking up the trip.

You could stay in White Sulphur Springs at the hot springs. It's pretty basic but it would be a swim break for the kids. Spa Hot Springs Motel & Clinic - Home

If you're coming through WSS at the end of July, you could also attend The Red Ants Pants Music Festival. It's a wonderful festival. https://redantspantsmusicfestival.com/

You could take a longer route and stay in Helena, but it would add about 2 hours.

Sorry, that's more like 8 hours, not 4

Check out Chico Hot Springs just south of Pray MT. They have lodging or try the day use pass. Another option would be a float trip down the Yellowstone from Gardiner MT.