The central coast will definitely be a cool place for you based on your self described profile. Since SLO is not on the ocean itself, you obviously will not be staying there if you want a beach front hotel. The Inn at Avila Beach (about 10 mils south of SLO) might be your closest option:
You might also try a few miles further south at the Spyglass Inn at Pismo Beach:
There are a few others in the Pismo area.
As for some activities over 5 days (in no specific order):
• Downtown SLO (especially during Thursday nigh Farmer's Market)
• Morro Bay (go check out "The Rock") and the wharf area. If you go to the rock, please make sure to go all the way back to where you are on large rocks and the ocean is coming all the way right to right below you by a couple of feet. Don't just stop at the front or side of the rock.
• Hearst Castle - a nice drive up the coast. You may want to even go further up to Big Sur (I believe there is currently a detour there which I am not keeping up on but a big active thread exists here) and Carmel and Monterey for the coastal drive alone.
• Paso Robles area (about 25 miles north of SLO) for wine tasting
• There are tons of places to go hiking and/or biking but I am not an aficionado so I will have to defer to others on what the great spots might be. Here is a link with some ideas:
• As for restaurants, I never miss a chance to go the F.McLintocks (though it's a steakhouse). If you go there, only go to the one in Shell Beach (their main one) as it is a long time institution of the area:
As for seafood, there are tons in that area but nothing that stands out for me. All of it is good just nothing THAT memorable. You'll run into plenty while you're there. This one has a very nice view and I did really like the lobster tail here a lot (but that is easy to like a lot).