Pacific Beach with kids
Pizza - Hoboken or I've seen a decent amount of younger kids at Woodstock.
Sushi - Ota is prime..but very expensive and would probably be wasted on the kids. Mister Sushi is still good enough, the rice for the nigiri is larger than I would prefer but the fish is..or if you're just looking for a place with rolls try PB sushi..it's loud, crowded, and there's drinking...but it's PB..you could be okay in a booth upfront.
Fish Tacos - Oscars Mexican Seafood - best in SD. It's northern PB on Turquoise street right where mission turns into la jolla blvd
Fish - FIshery..bit expensive, could also do the PB Fish shop
Asian Markets - on Convoy Street not too far off..nothing right in PB.
Pacific Beach can be trying at times with kids, mostly since a lot of options are designated as bars (no kids allowed) or are overtaken by the beach crowd (some parents don't like the exposure to the "whoo-hoo" crowd).
That being said:
Pizza - My top picks would be the Tap Room or Hoboken, but both are more "pub" atmosphere. My buddy swears by Ciro's, but I've yet to go. Naked Pizza has some interesting options, but is a chain, if you are looking to stay local.
Sushi - most sushi, near the beach in PB, is meh, at best. Surfside has half-price sushi on Mondays that is at least a good deal. Nothing else I've had in PB by the beach has been memorable enough to recommend. However, Sushi Ota, at the 5, is one of the most recommended sushi restaurants in the city and I have had many a good meal there.
Fish tacos - just go anywhere, they're all pretty good and each taco shop has their own little play on the final product. More notable places would be Oscar's, Don Bravo Bahia, Taco Surf and, yes, even Rubio's.
Fresh seafood - the Fishery, family environment restaurant with a wide range of choices and prices - I really appreciate the chef's focus on local, fresh produce to pair with the fish dishes. PB Fish Shop, fish sandwiches and beers in a neighborhood setting. I personally prefer El Pescador over the Fish Shop, but that is about a 10min drive north to La Jolla.
Asian Markets - none in PB, but every large asian market is about 15-20 drive, straight east, down Garnet, which becomes Balboa, to Convoy. Off the Convoy artery you will find Ranch 99 (Chinese), Zion and H-Mart (Korean), Nijya and Mitsuwa Marketplace (Japenese), and a bunch of others I am blanking on...
Have fun in my little 'hood!