You can get just appetizers at the bar. And children are "allowed"--although I confess I've never seen children at the bar there in all the times we've been going.
And to add that just getting a seat at the bar is something of a feat, especially anywhere near fireworks time.
You can order from the full menu in the lounge, not just appetizers. Not all the tables have a view of the MK from which the fireworks can be seen. The bar itself doesn't even face the windows.
This area is first come, first served. you can't make reservations for the lounge. The problem with that is, the closer it gets to fireworks time, the less likely you are to be able to get a seat, much less a seat from which you can see anything. You CAN access the outdoor viewing area if you are present in the restaurant during the show. Yes, children are allowed in the lounge. But unless you want to spend a few hours there, I don't recommend it as a way to do fireworks viewing. Especially for a family with young children, who may get restless having to wait.
If you eat in the lounge early (best time to get a seat), with your receipt you will be able to come back up at fireworks time and watch from the outdoor viewing area (not from a seat).
I've eaten at the bar at the california grill and found it to be quite enjoyable. It is first come first served and a viable option for folks who do not have a reservation. However, the larger the party the harder it will be to get a table etc there.
Full menu is available in the bar. I had a 4 course meal just myself there and it was phenomenal!
I do this all the time, as we like to do a monorail resort hop, with a visit and food/beverages at each. I'd just get there early and it shouldn't be a problem, and I think kids would be fine in the bar tables off to the side of the actual bar...