I personally like Dave's idea best - drive from SD to Sedona or Flagstaff without delay on Thursday via I-8 and around Phoenix, then arrange your sightseeing accordingly. Spend 2 days coming back and enjoy Joshua Tree, spending a night somewhere between Kingman and 29 Palms. You could take a side trip up into Oatman and/or Lake Havasu City as part of this - in fact, that could be a decent overnight. Yes, Flagstaff will be cold, but is more centrally located to be able to spend a full day in the Grand Canyon.

If you want to research Joshua Tree, spend some time on the NPS site. The rangers at the staffed visitor's centers are also very helpful. Be sure to click the "Things To Do" link.