When I was in high school years, I went with a college workshop the first few times since they offered food, a place for the sleeping bag, and 4wd access, but since then, I've traveled much of Death Valley on my own or with friends (for back-up vehicles venturing off the beaten path!). Since I liked back-country travel back then, didn't have the skills or the vehicle, it was a good choice.
Do your research, but stick to the paved/patrolled roads!
Most of the major sights that most like to photograph in Death Valley are along the major roads and with a few short graded roads to such features as Mustard Canyon, Titus Canyon, etc.
Some of the canyons, especially in the Panamint Range, sometimes The Racetrack, require high-clearance vehicles at the very least, and good preparation and sometimes a rugged 4wd with the skills to operate it. But most of the highlights are fairly accessible.
Your best time for the light is at the start and end of the days and during the rest of the day, you can scout, visit the museum, Castle, etc. and rest.
Most people avoid the summers, sometime around Memorial Day through Labor Day unless they are there to experience a 50° C. temp, otherwise the heat can get you!
Traveling blindly with just GPS can be an issue and a few people ended up dead! Winter can be quite cold and higher elevations can have snow, so be prepared, even with tire chains, nonetheless!
I think that many of the workshops will get you to the best places at the right time and that sometimes the social aspects of going with a group can lead to a great experience, but sometimes, it's nice to travel alone and in peace! Maybe you should consider a 3-4 day workshop, and a few days just to travel on your own.
Do some research of the places you wish to see, the things you wish to photograph and then see if any of the workshops will cover the bulk of your desires. If not, nothing wrong with winging it and lingering where you wish and changing your plans as the weather and your path will lead you.
Have fun traveling there, take lots of pix, kill only time, leave only footprints, but beware the long distances, weather issues, drink a lot of water, and watch (and listen) to the critters who buzz and rattle and give them room! :-)