Murray Beach Provincial Park in New Brunswick
http://www.tourismnewbrunswick.ca/Product.aspx?pid=1331
Clean, spacious, nice views.
Our site was electric only and cost $28 per night. Parked on grass. There were a few full hookups site but they were pretty close together and on a side hill so bring leveling blocks!
It is not far off the route to and from PEI so it is a good place to stop as part of a larger trip if you need to.