I cant find any mention of "WidowMaker Canyon" in any of my books or maps,so it may be an unofficial name. The location you mention is about 2.6 miles up a wash, from the so called Hole-in-the-Wall, which is really gap in the mountain range caused by water erosion. Dosent look like there is any trail to that location. The hike will gain about 2000ft in elevation. The 4x4 trail ended(closed by park) at a quarry about 2 miles from the gap.
Sounds like you have never been to DV. You will have to check in at the Visitor Center and pay the $10 entrance fee. If desired, the Rangers will talk with you about where you are going and one may be familiar with the location. Once you leave the Center there is a Chevron station, but dont think it is open 24 hours. It has gasoline,diesel, and bulk ice. Down the road is the Furnace Creek Ranch with store, restaurants ,bar etc.
The sign post is on the East side of road about halfway between entrance and exit (west side) of the "Twenty Mule Team Canyon" one way loop. Its worth the time to drive it . The trail is really a wash. Last time I was on it was end of November, and there have been several rains/floods since then. High clearance was needed and 4WD is strongly advisable. You cannot camp within 2mi of the main road turn-off so the gap area would probably be the best spot , about 3.6 mi. That is also the spot where you follow the wash up to "Widow". Area is patrolled by Rangers in vehicles and in the air on a regular basis.
If you want I can send a higher quality Topo image to you. Enjoy and please post an update of trip when you return.
Tom