Tricia,
Great choice! Here is what you need to know and do. First off, there are two basic rooms at
'Ohana. The main room, and the smaller side room. Make sure you ask for a seat in the larger main room. This will get you a better view of the fireworks, as well as the entertainment in the restaurant. Ask for this when you approach the check-in desk, and arrive extra early so that you can wait out getting one of these seats.
At the same time ask if you can have a seat near the windows, with the interest in watching the fireworks. They will know where to put you. There are no guarantees, but I have found the staff very accommodating!
Final thought. Check when the fireworks are scheduled for that day. If it seems that your dinner reservation will not get you to that time, consider heading down to the resort beach after dinner to watch the fireworks from there. They pipe in the park soundtrack, and it can be a great experience!
If I can help with any other follow-up questions, just ask me from my bio page!
Have a magical (and delicious) vacation!