Egen Lake camp ground is the closest official camp ground to the big dunes. It is west of Idaho Dunes RV camp ground approximately a mile +/-
It's a bit of a hike from Egen Lake to the best of the big dunes, Devils, Choke Cherry, ect. If you have a fuel guzzler you will need to pack extra fuel to make the ride too and from and have enough fuel to play on the big hills.
The big dunes there are an absolute blast to play on!!
Someone local will have to chime in on weather sand camping is allowed and on a source for race gas and riding double.