Hi Maureen,
I believe you're thinking of the
Top of the World Lounge at Bay Lake Tower. This is a lounge exclusively for Disney Vacation Club members staying at Bay Lake. If you are a DVC member, you would be welcome to view the fireworks from there.
The lounge is open from 5:00 p.m. until midnight every day. While it is located on the 15th floor, you have to check in on the first floor of Bay Lake to get access. You'll need to show your room key and possibly also your DVC membership card.
The lounge is very comfortable and relaxing, with plush couches and even a few little private alcoves. I've had dessert and drinks there many times while watching Wishes. What a treat! While there is a full bar at the lounge, you are welcome to order coffee or soft drinks, or even nothing at all.
Children are welcome, but my experience has been that most kids clear out as soon as the fireworks are over.
If you are not a Disney Vacation Club member, then you would have to find an alternate location to watch the fireworks. The California Grill and the walkway connecting BLT to the Contemporary are good alternatives.
Have a wonderful vacation!