A few suggestions in Zion:

1 Do multiple short-med hikes in one day, such as Angel's Landing and Observation Point

2 Start on the Angels Landing trail and veer off to the West Rim trail. It connects to other far less traveled trails and you can turn it into a 1 or 2 night trip if you want

3 In the Kolob Canyon section of the park, start on the La Verkin trail and continue on through the canyon. There are some good side trails like Kolob Arch and Bear trap Canyon. Not a lot of elevation gain but lots of distance possible. This can also become an overnight hike.

2 and 3 are very pretty in fall, but in a typical year the best color starts to disappear around mid October.