For slightly upscale seafood check out Waterbar, not in Union Square/Fisherman’s Wharf but not too far away, on the Embarcadero. You can possibly get a nice view of the bay there too, and they have a patio. They also have a happy hour with $1.05 oysters Monday to Friday from 11:30am until 5:30pm. They do close at 10 though. SF restaurants in general don’t stay open very late. They also open for lunch and take reservations.
Not strictly a seafood restaurant, but La Ciccia in Noe Valley has some really good seafood dishes, including a spaghetti with bottarga, a spicy octopus stew, and seared prawns. They also have a whole fish prep that I haven’t tried. Closes at 10. You didn’t specify when you will be visiting, but according to Opentable they are closed until July 21 for vacation.
I like Hog Island Oyster Co. for seafood in the Ferry Building (Embarcadero) as well for lunch or dinner. They don’t take reservations but the line usually moves pretty quickly though it can get long on the weekends. They also have some outdoor seating. They close at 9pm though, so maybe too early for your dinner.
There is also a newish place in the Financial District that looks good - Leo’s Oyster Bar - that I have been wanting to try but haven’t gotten around to yet. Looks like they are open until 11 on Fridays.
Other ideas for a seafood lunch (but don’t take reservations):
Anchor Oyster Bar in the Castro - good neighborhood place but no reservations and small. There will probably be a line. Can also be possibly dinner - closes at 10.
Swan Oyster Depot if you don’t mind waiting in line (also no reservations and small). They are closed until the 10th of July.