you are on the right track for some great things to do.
I have never hiked Seneca Rocks, but the sight-seeing alone is worth the winding roads. Canaan was mentioned and not too far from Seneca Rocks. It is a beautiful valley with nice cool weather. Check out Dolly Sods not too far from there.
The New River Gorge is incredible. My husband and I are fond of taking the one lane road that goes under the bridge and seeing the views from the bottom. Summersville Lake is my all time favorite and near the Gorge. Battle Run is a great campground but weekends are hard to book. I love the people at the Burnsville Marina, but the lake isn't much to see. Summersville will be much better and you can rent a pontoon as well as paddle boards, etc at the marina. The water is crystal clear and the rock formations pretty cool. Carnifex Ferry battlefield is nearby. We have never spent alot of time in the Northern Panhandle but it is a very historic region with thing like Harper's Ferry.
Pocahontas county is just beautiful country. You can check out the cute little town of Lewisburg in the eastern part of the state near the Greenbrier Resort in White Sulpher Springs. Not alot to do there that I know of. Maybe some tubing down rivers and just kicking back. There are hiking trails all over the state. Maybe search the Rails to Trails program. Try searching Greenbrier River.
Regarding trains...my husband is an excursion train nut. Cass is ok, but nothing special. There are several excursion trains that leave out of the Elkins area. (that is also up towards Canaan and Seneca Rocks.)
This state gets a bad rap but is filled with natural beauty. I have lived here all my life, but still find new things to explore on our Sunday drives. Lots of history here too. Search Mary Engles or read the book "Follow the River". Most of her journey took her through WV.
Enjoy!!!