John, I guess you know that it can be very hot there, even in May. There will be many more visitors there over the holiday weekend. However, most of them will limit their visit to the lowest and hottest part of the flat desert. Instead, if you get up into the surrounding mountain ranges, you will avoid the worst of the heat. You might even be able to find snow in the Panamints. In fact, you need to plan on cool windy weather once you get above 8000 feet or so. There are many places to go where there are so few people that if you die, your body won't be found for a long time.
I recommend hiking across the Stovepipe Wells Sand Dunes, but only very early in the morning (dawn) and finish before 10 a.m. However much drinking water you think you need to carry, double that.