Oooh, I am going to Clippesby this year, it's fab! you should be able to get in if you are going before proper school holiday season.
The biggest draw if you have children is that is is very close to beWILDerwood seriously one of the best places I have ever taken my kids (we go several times a year). The beWILDerwood team have also built a mini version at Clippesby itself.
North Norfolk generally is fab, huge beaches, nice little villages, fab pubs. I have been several time a year since I was born! It is my spiritual home.
Sorry.
Okay here are some things you can try
bewilderwood
Day in Norwich, city is lovely and Catherdral and grounds are amazing, we spent a day there last year with 2 3yo and they loved it.
Boat trip to see the seals with Beans Just amazing.
Day at Wells is bit of a hike, but worth it, park in town, get picnic stuff from the bakery and deli, get the little train down to the woods, picnic in the enormous, beautiful pinewoods, spend the afternoon on the beach, get chips from Frenchs (nowhere else mind) eat them on the harbour.
Day in Cromer slightly dilapidated but romantic, has a pier, funfair that is only really suitable for under 7's so perfect, beach, nice little shops.
Dinosaurs! Actually this is not my favourite, but I have just asked ds what else we like to do in Norfolk and he reminded me how much he loves it here, plus it is close to the campsite.
From Clippesby itself you can hire bikes/picnic in the woods/swin in the pool/lounge around checking out other campers equiptment.
Also good
Holkham hall has massive grounds a huge herd of albino deer and an amazing beach
Fakenham has a fab market of a Wednesday morning.
Burnham Deepdale has a gorgeous pub called the Hoste Arms, which is owned by a mate of Stephen Frys, who we have seen in there.
Old Hunstanton beach is lovely.
You had better sodding go now 
.