I don't know if you looked at that page of my TR yet (page 26, to be exact) with the Catalina pictures, but I actually added many more photos to that same page after I posted here yesterday, so there are several posts' worth of Catalina pictures. But if you looked in the evening then you probably saw everything.
The 'Casino' in Avalon is not that type of Casino. It is called that for historical and architectural purposes, but it is not an active Casino with gambling. In fact, in the Big Band days, Benny Goodman and all the big swing bands and singers in that genre played at the Avalon Ballroom. It is really pretty inside. Now it is basically a ballroom that is used for special shows and events. On the Casino tour, they walk you around and show you parts of the Casino that the general public cannot access and they give you history about the building itself and the Island in general. It is supposedly haunted, but who knows about that? It is a cool little tour to do.
I think the kids would like the golf cart - the best thing to do is take an early boat out from Long Beach and grab a bite to eat (there is a great place that used to be called the Pancake Cottage, but now is called the Cottage, and they make good breakfast food), then go to the golf cart rental place right near where the Catalina Express boat docks. That place usually has a rent a golf cart for 2 hours, get the third hour free deal. Even if you just get two hours, it is still fine. Then you get to drive all around up in the hills and down little side street, and get some great photo opportunies overlooking the ocean. You will see the Wrigley Memorial (yes, the chewing gum Wrigley family, who used to owed most of Catalina Island and the Cub practiced on the Island) and you can walk up to the Botanical Garden.
I also think the kids would really enjoy the Semi-Submersible (which is where my fish pictures came from) and if you stay until evening, which I recommend, they would probably love the Flying Fish Tour. If you have never seen a flying fish, that is worth it, as they come out by the hundreds at nighttime, when the tour boat shines a big light on them. The kids would also probably like the Cruise to Seal Rocks, which takes you out to a point where a lot of seals (sea lions mostly) congregate on these rocks in dozens. The Semi-Sub and the Seal Rock tours can be done in the daytime, as can the Casino tour, but the Flying Fish tour only runs in the evening, so I would suggest making a Catalina Express return time (back to Long Beach) for nighttime, after the Flying Fish tour.
Then, once you get back to Long Beach, it will take about 25 minutes to drive back to Anaheim.
There are also tours that take you into the interior of the Island where you can see buffalo (I posted one buffalo shot). Sometimes the buffalo ar right there along the side of the road and sometimes they are way up in the hills. But those inland/interior tours take a big chunk of the day, so those are better to do if you stay overnight or for a coulple of days rather than a one-day trip. But you can easily fit in a golf cart rental, and a few tours and a meal or two all in one day.
As for eating, yes, all the places are kid-friendly! There are walk-up/counter service places (Coney Island West has great chili burgers), there is a Coldstone Creamery, there is even a tiny KFC/Taco Bell (I assume it is still there). There is a small Vons supermarket. THen there are all kinds of good places to eat like Antonio's Pizzeria (great waterside dining and great menu), Busy Bee Cafe, Armstrongs Fish Market, the Cottage, and all kinds of other places. It is very kid-friendly.
I think you all would have a great time!