I'd suggest the coast. Avila and Pismo are OK. But in Morro Bay, you've got more possibilities. Montana de Oro and in and around the bay. You can rent kayaks and play around the bay some. Look for the otters. Some possibilities for sunset dining, etc. But there are also some nice eats in San Luis, too. You can go north from there to Cambria and San Simeon areas. Besides the town of Cambria and Hearst Castle, there will likely be elephant seals at Piedras Blancas. Mostly females and young ones this time of year. Not sure how far north you can go on Highway 1. It's closed in Big Sur. But you might be able to get some of the spectacular cliff edge driving. They'll be able to tell you locally how far you can go. Morro Bay and Cambria aren't too bad for gassing up, markets, if you want to grab something for a picnic, etc. Past Cambria the pickings are slim and expensive.
North of San Luis on the 101 you can go to Paso Robles for the local wineries although there are some in closer to San Luis as well.