I lived in Ottawa for 4 years so have a few suggestions.
1) Parliament Hill - make sure you book a tour as this inside of the buildings is cool, although I'm not sure exactly where tours go these days with all the construction. If they still offer an East Block tour, I'd highly recommend you do that in addition to the main tour if you've got an historical bent. They have Sir John A's office and Trudeau I's cabinet meeting room setup like they were in their respective eras.
It's also worth just wandering the grounds as well, depending on what's going on with the construction.
2) If you have a rental car (or even if you don't an uber/cab shouldn't be too bad as its only 20-30 minutes away) go to the Mackenzie King Estate in Gatineau Park. It's beautiful (both the estate and the Gatineau Hills), plus you'll learn all about our longest serving PM and his ... unusual ... spiritual beliefs. It's also close to the town of Chelsea, which is a cool little town with good restaurants.
Bonus - go to Champlain Lookout in Gatineau Park if it's a clear day - awesome views of the Ottawa river valley and it's a nice drive.
3) Museums - Ottawa has tons of high quality museums, not just the main ones (Civilization and War museums). The Nature Museum is a cool building to see and geared towards kids, the National Gallery is great if you like art. Here's the full list, they're all really good even if the sizes vary.
https://ottawatourism.ca/en/ottawa-i...tional-museums
4) Ottawa has cool architecture so it's worth walking around. If you're staying at the Fairmont, you could do a couple really cool walks. One would be to go down past the locks, behind parliament then back up the other side of parliament hill and back along wellington. Another is down the canal and then back through centre town and the glebe along the main roads.
5) Food - Ottawa has a good food scene if you do a bit of research on what places are decent.
Have a good trip.
