If all of you are going (I see from your signature that there are 6 of you), you are probably not going to get a table where you can watch Wishes from. We've been about 20 times and have only been able to watch Wishes once from our table and that was because for that trip, we were only a party of four and finally got lucky. The tables along the windows on the castle side are for small parties and most of the tables have such a glare on the windows that you can't see well from them anyway.
Last time we ate there, which was last month, we had to stand in their very crowded little lobby area for 70 minutes for a table to open up. That was 90 minutes before fireworks so we actually got seated at 20 minutes till fireworks and we had just received our appetizers when they started. It seems everyone has caught on to the go early and order appetizers and extend the mealtime out to stay for the fireworks.
The food is very good, which is why we go (we love sushi) but I would not go here just to watch fireworks. I would say make your reservations for about 2 hours before the fireworks. Plan on a long evening. If you haven't eaten here before, enjoy the food. The sushi selections are the best items on the menu.