Depending your kid's interests, you could do a day trip rafting the McKenzie River, drive a few hours over to the coast and check out the Pacific Ocean, or do a hike to the one of the many hot springs around (
https://www.eugenecascadescoast.org/blog/post/guide-to-hot-springs-in-the-cascades/)
Another option would be to drive down to Ashland and catch a show at the Oregon Shakespeare Festival, and then do the Oregon Caves or dip into Northern California for some redwood time.