Look at your past use of the boat -- if you spent most of your time fixing the boat (like I seem to do), or sitting on it after work, position the boat close to home. If you sailed every weekend for overnight trips and you have a lust for adventure, then position her on Lake Ontario or in the Thousand Islands. Brockville lies on a narrow part of the river and it is a jog to get to more open water for longer sails. Kingston would be great but is a relatively long drive from Ottawa.
Also, do not underestimate the drives in Ottawa or the surroundings -- you will contend with traffic depending on your schedule.
Were it me I would consider a compromise -- plan on two to three seasons exploring the upper Ottawa river. Then, if schedule and logistics permit, shift the boat down closer to Lake Ontario.