I ate at both places during my '09 trip, although the visit to Fulton's was lunch, OOP (our first stop other than the resort, actually). I loved being able to look out while it was still daylight. Fulton's is at the top of my mother's list of places to eat at when we get around to returning to WDW. I can't really say what dinner is like there, but if it is on par or better than lunch, it's worth serious consideration.
Later that trip, I did do the California Grill for 2 table credits to watch Wishes. The menu was a bit exotic at the California Grill. I seem to recall ostrich being one option the evening I went. I don't recall what I ate, but it wasn't that. My table wasn't in a room with a great view, but I still enjoyed the atmosphere. Even though I couldn't see Wishes from the table, we were permitted to relocate to where we could (complete with audio). All in all, it was a nice evening. It's not likely that I'll do another dining plan with table service, but if I did, I'd personally give the CG consideration.
Looking back to my trip, there is no guarantee that you'd get a table with a good view at California Grill, and your younger sons might not be able to get a good view of the fireworks from the outdoor viewing area due to the protective wall (unless there have been changes in the last 2.5 years). On one hand, if you could snag an ideally located table, it would be a great memory for the boys. But if you can't it, they might not enjoy it as much.
I know I don't really answer your question, but I hope I've given you something to think about. My suggestion is that you do Fulton's this trip and make California Grill a priority on your next one. Or else do what we did and do Fulton's for lunch, CG for dinner.