I'd agree with the earlier ADR. Although a 7:30 seating seems early to watch Wishes at 10, meals seem to take a while at California Grill.
Also, be aware that a 9:20 ADR doesn't mean that you'll actually be seated then for dinner. People tend to stretch out their meals so they can watch Wishes, so the wait is long. If you get seated at 9:20, you probably won't even get your appetizers until Wishes ends!
I've had a MK view seat and would say that the observation deck is better for viewing. The music is piped inside and out, so you'll be able to hear the theme music.
I don't remember the lights being completely dim inside, so there was some reflection in the windows while watching from the table. Very distracting to me.
If you finish up early, you can hang out, relax outside on the observation deck (there are two, and the one that's near the bathrooms is much much less crowded). Or you can go downstairs, shop a bit and go back upstairs-- they allow you to go back up and watch the fireworks if you've eaten there that day.
Definitely mention your anniversary surprise when you make your ADR.