Monnytink, my understanding is that when a presidential building is booked by an owner, it is for a specific unit at the time of booking. The owner should be able to tell you the unit number of the unit he reserved for you.
In building 6, the odd numbers face the lake, the even face the conservation area and towards Downtown Disney. Building 5 does block the fireworks view all the way to the top floor, 19, for some units because building 6 is curved like a partial crescent shape, and Building 5 blocks the view of all but the highest fireworks. However, the view of the lake and especially the sunset over the lake is wonderful. I was in 1919, 2 room presidential, a few weeks ago and could see (from a distance) the Dolphin hotel, Tower of Terror, the rooftops of the Carribbean beach all dead on, and Pop Century to the left. I also could see part of the Hilton Bonnet Creek building even further to the left.
You could not see the castle (way too far away) nor Space ship Earth from the unit where we stayed. I actually never saw the fireworks from Fantasmic either but I think I was either not in the room at the right time or Fantasmic was cancelled due to rain.
We did stay in a 3 bedroom end unit in building 4 once where we were able to catch Illuminations and see fireworks during Fantasmic, but it was a deluxe unit not a presidential.
Hope that is helpful.
I do think there are some units in building 6 where you can see fireworks, perhaps the end of 6 that just outs past building 5 on the far end of the crescent curve of the building. Maybe the resort can advise you.
