You are going at the perfect time of the year. I lived in Anchorage, and spent my summers on the Kenai Peninsula. Therefore, I am only able to give you insight on those areas.
One of the most beautiful places (on a clear day) to see the Redoubt and Iliamna Volcanoes is from the beaches on Clam Gulch (about 15-20 miles south of Soldotna.) Or, even a little further down on Anchor Point. There are little cottages that you can rent off of the Sterling Highway (close to the water,) which will allow you to walk down to the water at night and see, probably, the most beautiful sunset you could ever witness.
As far as hiking trails go, they can be found all the way (up and down) Highway 1, and I would encourage you to veer off (on Highway 9) to visit Seward for a day…another beautiful place.
Hope this was helpful, and enjoy your trip…I am extremely envious!