Don't remember taking our dog (RIP and the only one we had in Norfolk) to the broads, Sen. N Norfolk coast was the place for us and Misty loved the sea.

I think the best (but, on reflection, risky and I can't swim...) we did with her (purely as a one off and our only longer walk) was a walk from Cley to Blakeney and far enough on the sands to see the seals. Our timing was good and we kept a watch but the water comes in behind you quickly there.

More mundane but my favorite place was probably Trimmingham