mate, try willowgrove@bestonparks, thats the caravan park at Benaraby, bout 10 mins from the dam.
Plenty of room down the back to set up a camp, they also have cabins etc.
Bonus is they have their own ramp straight into the salt water side of the Boyne, gives you another option.
I would stay away from the caravan park at the dam, we have been double booked there our selves, plus I know others have had problems.
No worries with the ramp at the dam, 2 lane concrete, just a long way to reverse cause of the low water levels.
Parking can be a problem due to crowds, I beat that by being on the water at sparrows.
hope that helps
cheers
Brian