Oh man, that is my home! I grew up in elkton and have hiked all over SNP. First off Massanutten is at the end of the national forest and theres forest service roads to drive on you can take them all the way to grovehill.
Shenandoah national Park would be your best bet, for all sorts of hikes and what not. It does cost to get into the park, you can get a day or week long pass for the park. You would come in at the swiff run gap entrance. It is in the middle of the park. The southern part of the park has more wilderness and less big campgrounds. It was always my favorite part of the park. Two of favs places, are hightop mountain and blackrock. Very easy to get to. The central and northern parks has the larger campgrounds. Big Meadows is the most know. Also lots of day hike places there. Also the AT runs the entire length of the park South to North.
For trip planning theres an outdoor shop in harrisonburg called wilderness voyagers. You can get some maps there of the park. I would suggest you get the Potomac Appalachian trail club series of maps, north, central, and south district. These are really good maps and cover the entire park and has pretty much everything in the park on it. I used these maps for all my travels in the park. They have a website that I think you can get them form there before you get to the AO. Also theres a book hiking Shenandoah national park(I think that is the name.) Its had tuns of day hikes in it. Got mine at wilderness. You can also get trail books at different places in the park.
Sorry I dont have better info on the books and maps. I dont have them here in pa, they at my moms(in elkton). Be sure to stop buy cerios in elkton have steak and cheese sub for me.
I havent been home in a few years, Im jealous that you are gonna beat me there. Please take pictures and post them. If you have anymore questions just ask and I will do my best to answer them, HTH-Chris