How long are you going for? Unless its just a few days I don't think there is anywhere big enough to have somewhere different to eat each night - there are some lovely villages but they are teeny tiny!
Seahouses is among the larger ones, it has maybe one nice restaurant but mainly fish and chip places.
Bamburgh might be a good alternative - some good pubs and little shops. Your in laws could go to the castle and on walks.
You might have to venture out in the car to find more places to eat but there are lots of villages close together so it is not as if you will be traveling for miles. Some places to eat:
There is a good pub in Embleton, and the golf club there does nice bacon sandwiches - good after a walk on the beach.
The pub at Low Newton by the Sea is lovely too.
Eleanor's Byre near Embleton, on the road to Craster, has a nice cafe and little gift shop.
Sunnyhills farm shop in Belford is nice but inland.
Get kippers from the smokehouse in Craster. The walk from Craster to Dunstanburgh is fab and not very challenging.
This website has some gorgeous self catering places but they are a bit ££££!
www.coastalretreats.co.uk/