Hello. I am not sure about the actual ceremony, but I would highly recommend the Hotel Dominion 1912 for accomodations (in their new section). Although, there is no actual restaurant in the hotel they have a very Romantic lobby/sitting area where they serve an amazing free breakfast each morning. Seconds away from the hotel are tons of fabulous restaurants. The hotel staff are very helpful and I have a feeling if you called to make reservations they could steer you in the proper direction regarding the actual ceremony. If you wish to read more about the hotel here is a link to my review with ten pictures I took. I hope this helps.
Perhaps the Ursuline Sisters rent out the chapel that they must have in their convent in the heart of the walled city.
Otherwise, anywhere but out in the middle of the Plains of Abraham under the big wide sky (not joking here) you're likely to draw a crowd. The Gardens are lovely, but you definitely would draw a crowd. Out on the edge of the plains, you would have a memorable view of the river, and most of your neighbors are so into their own thing that they wouldn't bother you if you aren't bothering them. The big issue would be having a rain Plan B place. And the more remote the place on the plains you might choose for the nuptials, the more of a scramble you'd have, in the event.
Plan B (or Plan A) could be the gazebo-like observatory by the plains' upper parking lot. Maybe those responsible could be requested to allow only the wedding party into it during the wedding.
Maybe on the parade grounds of the fort.
Really, except for the image of the possible scramble in full regalia, this is in all seriousness.
Maybe the Quebecois here can comment as to whether these things are ever done.
(Mistrosmom, boy does that Hotel Dominion 1912 look like a fantastic place to stay.)
The sweeping landscape of the Plains of Abraham would be beautiful. There are numerous areas including the Jardin St Joan of Arc which is a beautiful sunken garden filled with flowers and shrubs. Also many panoramic views with the St Lawrence River in the background and the old buildings of Le Citadel. The Ursuline Chapel is quaint, not sure if you are going for a religous ceremomny.
P.S. In a park in front of the Parliament Building is a nice wrought iron gazebo that would be nice and somewhat private.
Thanks for all the replies! The Clos St. Louis certainly looks cozy & romantic and gets excellent reviews, but we had already booked at the Dominion, which was our first choice and also gets raves reviews. We're actually looking for a ceremony location and other suggestions for the big day (photographer, flowers, hair, original dinner ideas, etc.).
I will definitely contact La Marieuse - I was having a hard time finding a planner so have been counting on the officiant and the hotel concierge for suggestions. So far we've been considering the Parc des Gouverneurs and the rooftop of the Musee de la Civilisation (any thoughts?) but I will look into all of your suggestions.