A camping forum for VW bus and camper owners.
Fifteen years back I took a group of 4-H kids to spend the week in Death Valley for Easter Break. Now, I will admit that it snowed on us that week, but if you look at the Death Valley Park website you can see that the typical weather in April is a high of 90 and a low of 62 degrees. http://www.nps.gov/deva/planyourvisit/index.htm
Stop by Calico Ghost town on the way past Barstow and then on into the valley.
Once there the kids will really get into all the usual, especially Badwater, Marble canyon, Scotty's Castle. As long as you have confidence in your rig, drive out to the Racetrack, and definitely out to the ghost town of Rhyolite in Nevada (just outside the park) and then back into the park through Titus Canyon. The Sand dunes, Darwin Falls, and Wildrose Charcoal Kilns are all great places to go.
Great time of year in the park; temps are comfortable, crowds are not there, and if the winter times just right for you the desert should be green and flowerful.