The nights are cold with possibility of more rain and snow in January and early February. Early March is my vote. Later in the season the more the snow melts in the high passes also. Plenty of room in DV. While you will stop at some common spots on the paved routes, the dirt routes are wide open. Easy to spend 2 weeks there with a different destination each day. You might plan on changing locations a few times. It is a long ways between destinations within the park, you might not realize just how big that place it until you drive it yourself.
I would split the trip into 3 or 4 zones, say north, south, west, and east, and move through them in an orderly fashion. You will save a lot of gas and drive time over the same main access routes. You can build a few very long loops. Note that Titus Canyon is one way. There are specific camping rules that apply regarding distance from certain roads or any road that you need to study. The main campgrounds are usually full but you might find the odd cancellation especially in the tenting areas. Some restuarants and facilities near StovePipe Wells and Furnace Creek. Can get water, RV dump, and bathrooms there for mid trip services.