Hi and congratulations, there are so many beautiful places... Have you looked at monies bay? sorry not sure of how to spell it, but not only does it have a beach but they have a garden area, with a Japanese style Bridge, and weeping willows trees, Or The experimental Farm in their gardens, I know its a place loads of weddings get their photos
Rockliffe Park Pavillion is so beautiful - we considered it highly, but did not select because of the trouble to organize... We married outside at Greyhawk Golf Course. they have a wonderful staff there that helps with everything ;)
Rockcliffe was the best choice for us! We had a great view of the water, some green space for kids to run around and smokers to do whatever, and we had a built in rain plan!
The only down sides are the limited parking, and the fact that if you don't know Ottawa, its somewhat difficult to find without a GPS.
You just have to get creative with the organizing...we had a boombox for music, very simple decorations, and our only vendor was for the chairs. Everything else we did ourselves. We had a a 45 minute ceremony, and then we hung out and took pictures before leaving for our reception.
Its a popular site so there are likely to have other weddings before and after yours (each wedding gets a 4 hr timeslot only) so you have to vacate as others start to arrive to set up their wedding.