I know this is a little late, but maybe you can use it for this upcoming year. I recommend strolling out to any of the bridges between Ontario and Quebec. My parents claim the Island Park bridge is even a good view, but I’d probably go at least as close as the one by the War Museum at Lebreton Flats or that scary old train bridge a little to the west of it. Shouldn’t be too zany around there.
Alternatively, if you can snag a rooftop in Sandy Hill, or Ottawa U you probably get a decent view. That isn’t really downtown, is it?
Some people choose the Quebec side, over by the Museum of Civilization, but if you’re looking to avoid cars and crowds, it probably isn’t what you’re looking for.