There are a few places I never miss in San Diego...
http://www.gofishanthonys.com/
Anthony's Fish Restaurant. It's really good, both the fishette and the sit down restaurant. The sit down is right on the harbor, so if you plan it right you can watch the sun set over the ocean.
http://www.seaportvillage.com/
great unique shopping, great salt water taffy
http://www.amwest-travel.com/awt_sdseal.html
Children's Beach is covered with seals to watch
http://www.califmall.com/beach/BchSanDiego.html
San Diego beach and other resource page
http://www.balboapark.org/calendar/detail.php?EventID=370
Balboa Park (where the zoo is) has TONS of neat museums. Some museums are free on Tuesday; this is the free Tues schedule
http://aquarium.ucsd.edu/
Scripps Aquarium is really neat...
There are a few outlet centers not too far from the zoo.
You can spend all day at the zoo just in front of the monkey and gorilla exhibits and not even realize it. The pandas is a LONG walk downhill down a STEEP hill. Make sure you plan accordingly; it is tiring to do at the end of the day. Remember the animals are awake first thing in the morning and then late into the evening. The zoo has late summer hours, so you can always get your hand stamped, skip out on the afternoon when the animals are asleep, and come back.
The kids meals are HUGE. It's more food than my child can eat, but it's the perfect size for an adult. They get a hamburger, small drink, raisins, cookies, and something else, I think. I can't remember right now. DH and I have gotten 2 kids meals and split them between our 2 kids and us perfectly fine. The adult meals are XL, too. You and your husband can easily split a hamburger or sandwich unless you are big eaters.
have fun! August isn't that hot usually in San Diego, but it can get a bit warm right after lunch. In the late afternoon an ocean just as expensive as breeze usually picks up and that is refreshing.