If you would like full hookups and other creature amenities your best choices would be in Pahrump Nevada to use as a base camp then explore Death Valley from there.
Best time of the year for us has been in the spring when the "cactus is in bloom" or in the fall. You really don't want to be out on the salt flats at Bad Water in the summertime when it's 120+ and sun's ray's are bouncing off the white crystal salt cooking your face while blinding those without heavy eye protection.
If you go take lots of water as even in cool temps you'll lose body moisture through your skin pores as it's that dry out there.
There are a lot of fun things to do and places to see.
Just a heads up, the Valley gets a little crowded when the 49'rs hold their annual Encampment there
Bert