Limpets are tough: eat raw or cook for an hour or so with greens in a stew.
Mussels? I'm a Belgian, we eat thousands of tonnes of the stuff in this country. Have herbs, sliced onions and minced celery stewing in butter (some salt, pepper), when soft, add all the mussels you like and put the lid on. three minutes later, the mussels will start to open. Shake vigorously. Give them another minute and serve, any second over that will ruin them. enjoy and carefully remove the little pearls from your mouth when eating, your daughter will love these
Razors. Marinate in herbs and (olive) oil. Grill on the hot barbecue for about 17 seconds, turn (9 seconds on the other side). Serve with plenty of white wine. They taste like calamari.