Best first post ever!
Sounds pretty tight to me. Assuming your flight is on time, the helicopter isn't impeded by weather, there's no significant wait at 1 Centre (which is the city admin building across the street from City Hall--not City Hall itself) for the license, and each of you, your beloved, your officiant and anyone else who will be with you will be wearing good walking shoes (and physically capable of walking a couple miles over a few hours), you can probably do it. But if any one of those assumptions proves false, it may throw a wrench in the whole thing.
As for logistics, I'd take a car service from the heliport to 1 Centre and then have them pick you up after the ceremony to take you back to the heliport, and I'd recommend doing the rest on foot. The only other question is where exactly to have the car waiting for you near the bridge, since they can't pick you up on the bridge itself (I'm assuming the ceremony would on the bridge itself, not just in view of it).
And if you tell us exactly when and where, you can probably drum up some witnesses from this forum.