You can access the Rideau Canal right from the hotel. We love biking and walking down the pathways (and skating down the canal in winter). Bike rentals are nearby downtown, and it is approx 7km to Dow's Lake and back. But there are plenty of connecting trails if you want to explore more of the Ottawa River, Dow's Lake, the Experimental Farm, or the Dominion Arboretum.
Dow's Lake is where most of the flowers are for Tulip Fest (which happens in mid/late May, and you may just catch the tail end of the tulips in early June)! Last year, they also added some recreational docks, breweries in the parks, and there are restaurants nearby with sunny patios overlooking the water.
The wedding venue is right next door to Byward, and there is plenty of dining and shopping within 10 minutes of walking distance.
On the other side of the Rideau Locks is Parliament Hill!
Come see where the Ottawa Redblacks play. You can see into the stadium even when there are no events. Lots of shopping and restaurants here as well. Expect to take a 10-15 minute Uber.
Beautiful park nearby downtown, and great for driving through or hiking if you need some outdoors time. Chelsea is a cute town within the park, and is home to the Nordik Spa and a few restaurants. Expect to take a car here, unless you want to do the 2 hour bike ride from downtown!
If you're looking to extend your trip, we would suggest a quick tour to the Thousand Islands. It is approx. 1 hour drive away from Ottawa and is a beautiful place to rent a boat for the day or drive through the 1000 Islands Parkway.