Is your van 4x4? If so...
Coyote Canyon and tributary Sheep Canyon & Cougar Canyon should fit in nicely with your schedule. This is one of the nicest places in Anza Borrego state Park ABSP
Sheep Canyon Camp 33.365494, -116.478984
Has it all: Water crossings, palm oasis, waterfalls, grottos, caves. After all the rain this year the waterfalls will be booming. Google "Sheep Canyon ABSP" if my links don't work below.
The road gets rough after the major water crossings, for about 3 miles up hill. That bit is challenging but not over the top. This part weeds out the timid SUV, Subaru, Lexus types. Keeps the crowds down. Easy after that. I've been back there in various 4x4 and a baja bug. Forum member PETE has taken his 4x4 SMB back there several times as well. I highly recomend it!
Sheep Canyon | San Diego Reader
Sheep Canyon Campground - Anza Borrego SP - NextCampsite