We have used the Park and Fly at Hunt Club (Uplands) in the past as well (before our 2 year old came along). Their shuttle runs very regularly (about every 10 minutes) and they offer a CAA discount. I think they are running some pretty good summer promotions right now.
With the recent upgrades to the Ottawa airport the long term parking there is very much competitve with offsite --- basically the same rate (but no discount offers).
If it were just my DH and I, I'd choose the Park and Fly for the discounts but with our young one I think I'd choose the Airport long term parking since you wouldn't have to load your luggage onto and off of the shuttle. (Both the airport and the Park and fly have their rates posted online.)