I'm here now, staying thru Aug 10. So I may be able to help a little bit.
Also, on the "trip reports" board there are a few OC locals who have provided a good list of places to try/eat. You're right that many don't survive, but there are also some long-standing traditions at OC that you can bank on.
Quick question - are you staying north end/gardens area? Central OC (from about 6th to about 20th) or south OC, from about 20th to the south end?
We're in the Gardens/north end. Sadly, we don't have many seafood lovers in our big group of 20+ - but, we do have kids - right now 6 kids under the age of 8. So we know kids ;)
As for seafood, in the north end is the Island Grill
http://www.ocnjislandgrill.com/ that I have not tried myself, but others in the clan have and enjoyed. It specializes in a VERY wide range of seafoods and is very casual yet not fast food. The crab trap
http://www.thecrabtrap.com/ back off the causeway to Somer's Point is the seafood standard in the area, but is also one of those giant 300 table places. So you get safety but not something all that "special".
Just south of OC is the Deauville Inn
http://www.deauvilleinn.com/ on the bay. Like the Crab Trap, it is a giant landmark of a place with decent but not necessarily inspired food. It does have good bay views and kids aren't a problem there.
If you are willing to take the drive to the north end of Cape May, (40 minutes on the Garden State Parkway, 90 minutes on the "gull route") try the Lobster House
https://www.thelobsterhouse.com/shop/Lobsterhouse.htm it is probably the best of the three, with really interesting views (and outdoor seating on the commercial pier!) and decent meals. It is also a giant landmark, but hey, there's no such thing as a bad trip to Cape May.
As for other stuff:
For Italian takeout, Voltaco's
http://voltacositalianfoods.com/ is your best bet, right behind the McDonalds as you come off the causeway onto 9th street. They have no tables, it is totally take out - but just awesome and no worries about the kids bothering others.
For pizza, it's Mack and Manco's
http://www.mackandmancos.com/ from a few locations, all on the boards. They are my favorite, although this is the jersey shore and I doubt there's any "bad" pizza anywhere.
For ice cream, like pizza, it is on virtually every corner and how bad could it be? and if it isn't on your corner - sit tight, a truck will come by soon enough with icecream on it.
For breakfast, we've been multiple times to the Chatterbox
http://www.oceancitychamber.com/businessdetails.asp?id=92 and to Uncle Bill's Pancake House
http://www.oceancitychamber.com/businessdetails.asp?id=461 (I can't find their official sites) and I have to give the nod to the Chatterbox. It is noisier from the kids, less expensive and pretty good overall. Bill's isn't bad - and the Cape May Bill's is a neat place to eat. But the chatterbox is my choice in OC.
As you might imagine, with 20 people and so many kids, we don't go out in OC much. But my wife and 2 kids will sometimes break from the pack and try places.
Tomorrow we'll be trying a few places and will report back. In the meantime, I hope this helps. And I hope you have a great time.