The thing about flying out of Ottawa is that there aren't a lot of direct flights into Florida, and the few that do exist tend to get very expensive very fast. And if you have to connect out of Ottawa, your total trip time is probably not much different than driving to another airport 2-3 hours away. Even if you have to drive 4-5 hours it might not make much of a difference to your trip. I find that unless we're on a very early or very late flight (neither of which I care for with kids in tow), you're pretty much killing a day on travel in each direction anyway.
We're in west end Ottawa, and last year we actually flew out of Buffalo. The travel times suited us and it was $1000 cheaper than any reasonable option out of Canada. It's not my first choice, but it was fine, and I'd do it again under the right circumstances. We've flown out of Syracuse in the past, but I've found that in recent years the flight prices out of Syracuse during Ontario school breaks tend to be inflated relative to other US airports, even on newly released flights. This year we're flying out of Montreal; with the abysmal exchange rate the savings out of the US airports was not worth the extra driving time. I can't remember ever flying out of Ottawa into Florida. Well, maybe once, twelve years ago, when there were only two of us.
We're paying to park no matter where we fly from, including Ottawa, so that's not really a big factor. The smaller US airports actually tend to be cheaper for parking. It's also a bit easier to cross the border by land instead of dealing with customs at the airport.
I wouldn't consider NYC area airports. Too far, too expensive to get there (tolls) and park, and the flights probably aren't even cheaper than the other US airports, though you'll have more direct options. If you can't find anything that suits you in Syracuse, try Rochester, Buffalo, or Albany, or maybe even one of the New England airports (Burlington, Manchester, Hartford). Whether or not it's "worth it" is a very individual equation.