Route Suggestion

Have you looked at plugshare.com for charging options. There is one listed at Massanutten.

As CHRGIT says, Massanutten is listed as having places to charge. They don't have actual chargers, but it's listed as having a 14-50 outlet which you can use with your UMC. I would call ahead to verify that it's in working order and you can use it.

Plugshare.com is in general a really useful resource for these things. There's a wide variety of chargers and situations out there so you can't just trust the marker on the map. Click them and look at the additional info to judge if you'll be able to use them. They also have a dedicated web site just for the in-car browser. Google "tesla plugshare" to locate that. It's slow, but it works really well and can be handy to have while out and about.

If you can charge at 240V at Massanutten overnight then this will be easy. I would do a range charge before you go (set the charge limit to 100% 60-90 minutes before departure, don't forget to set it back to 90% or whatever afterwards) just to have some extra margin, but the range is well within what your car can do. Check out EVTripPlanner.com for a more accurate view of exactly how much battery capacity the trip will take up.

If you can't charge at 240V at Massanutten then it's going to get tricky. I'd try to at least plug into 120V while there, which should give you 50ish miles of additional range overnight, then plan to spend some time exploring a town with a J1772 or HPWC on the way home. There's a residential HPWC in Staunton listed on PlugShare which could be a nice stop for a while. Look at alternative routes which are a bit slower but shorter. For example, it looks like taking route 219 to I-64 adds about 15 minutes of travel time but saves about 25 miles of rated range over going straight to I-81. Not important if you can charge fully overnight, but useful if you can't. Although if it ends up this way I would try really hard to buy or borrow a CHAdeMO adapter before your trip, which would make things a lot simpler.

If you get in your car and put the destination in your navigation system, the car will tell you if it can make it to your destination and how much battery percentage you will have left. If you cannot make it on a single charge, your car will provide you options to charge. You can also use PlugShare as rtkaul suggested. You can also go to EV Trip Planner, put in your car info and as such, and see if you can make it without a charge. I found on my cross-country trip (7200 miles!) the evtripplanner is conservative by approximately 5%, so if it says you can make it, I would believe it.

Here's an example of a Model S with 19" tires, 68 degrees inside temp (a/c on), 80 degree exterior temp, 200 pound payload (just you!)
Distance 219.7 miles
Driving Time 3:28
Total Energy Used 66.6 kWh
238 RM
Average Efficiency 303 Wh/mile
Net Elevation Change -564 feet

At 238 Rated Miles, if you max charge at home, you will have plenty to get to Massanutten, but you will have to charge there (abviously) to get anywhere after that (like home!)