I think shooting from home with ur camera on tripod aiming the tv will get you the best view...
On a more serious note, I doubt there will be any of those public accessible area without crowd if you want to shoot the ndp fireworks. Afterall, it's not the first time fireworks is held in this area. If there are any ideal location, it would have been identified by photographers and or public.
Oh, if you reaaaallly want to shoot the fireworks, consider reaching the ground before the crowd arrives.... Which is probably about 2pm or earlier... Still it will get crowded after sometime and it will be up to you to prevent yourself from getting squeezed or pushed out etc...