First thing I would tell you is Don't plan a trip to Dumont during the summer! It's friggen hot as like in mid 115-125 degree range. Secondally the wind shifts during the summer and dumps all the soft sand onto the back side making the dunes extremelly dangerous and it's very hard to see due to the angle of the sun being straight up all day= no shadows.
I would take it to St. Anthony's , Idaho. great dunes, can be warm during summer but not near as hot as death valley in summer.
Try contacting Mike at Idaho dunes RV park for more info. Great dunes, a lake and lot's of other things to do in the area.
Terry