Sandy beaches over at Heacham and Hunstanton. Amazing sandy beach at Holme. Google images will give you some ideas.
All of that coast (across to Cromer) is very good for touring although not all places have vast beaches or sandy beaches. East and West Runton are good with rock pools and the like.
The villages along the coast from Sidestrand down to say Happisburgh are not so good (and that includes Mundesley), but once you get to Sea Palling, Horsey, area it gets better and some beaches are superb.
A particular favourite is Winterton-on-Sea. Google images to get an idea and the village has a website too. Lovely village, lots of dunes, amazing beach that goes for miles each way. Just up the road from Hemsby, Scratby, Caister, Great Yarmouth but nothing like those places at all.
http://norfolkcoast.c...lk_wintertononsea.htm
Selection of cottages on here, but many more if you have a search around. It's a smallish place with lots of holiday lets, many alongside each other so with such a large party you may need to consider having 2 houses.
Best of luck.