Coast and Castles Boulmer. 

Proctors Stead Caravan Park

It’s a little odd, cos it’s C&CC (wilkomen, for you ze trip is over!), but the setting of Dunstan Hill campsite at Embleton in stunning. It’s quiet, clean and the walk down the bay is really nice. Good pubs and food in the village too. Just don’t stray too close to the fence or you’ll join Hilts in the cooler. 

What Drac said, often have a pizza van and beer options onsite as well. Plus it has bonus views of an F4 Phantom at Boulmer.

Annstead Farm is a (working farm) campsite, 20 seconds walk from the beach between Beadnell and Seahouses, I've stopped a few times with the camper. Good walk along beach to the golf club and chip shops of Seahouses.

Proctors Stead is a nice site but I'm sure they don't take tents now? Very handy for walks down to Craster and Dunstanburgh Castle

It has been over a decade since i lived there but they used to take tents. When the kids were little I sometimes took them there on a camping adventure. Drive around for 30 mins and turn up there no more than 3 miles from home. Tent up, long walk, feed in the pub and in bed with the dusk. Simpler times.

I think they still do at Proctor steads but Northumberland is a lot busier now, still relatively quiet to other areas but so much busier.