Amber, we are neighbours--Hammonds Plains here.
Westjet and Air Canada both recently had discounts on, and I checked them out. It was roughly 2k (maybe $2200?) for 4 of us from Halifax, plus about $1500 US for a similar package to you're talking about...a week at Pop for 4, with free dining and basic park tickets. (My ds will need 10yo tickets this time, but we're not getting hoppers.) So that's pretty much what your TA said.
You've probably got a decent price. I just hate to pay air from Hfx, as others have said. We have flown through the US twice now (and drove to Boston once in addition). Last time it took us 14 hrs to Manchester NH, where we got return tickets for 4 on Southwest for just under $500 US (for all 4, taxes in)--even with some road food and a night in a hotel, it saved us major cash. 14 hours is longer than most would take I think--I do think we've done it in 10. That time we stopped a couple of times for food, took a slight detour to dh's sister in Oromocto...(And that was January, but the roads were very good.) Lots of people go through Bangor or Portland ME, which takes a couple of hours off; probably not quite as cheap as Manchester, but still, I'd estimate you'd pay 1/2 or less of the Cdn fare. We bought a portable dvd player for the kids, I pack snacks, and heck, they're going to FLORIDA, so they'd better no complain too much.

The first time they did the drive they were 2 and 4. Dh and I LOVE road trips, though; if I don't let dh drive getting there, I'll have to spend the vacation putting up with him finding places to explore by car!

Some people just don't do road trips, and that's up to your family, of course.
We are hoping to go in September also, and I may use my airmiles to do it if I can, b/c I know the drive adds 2-3 days to the trip overall, which is fine when you've got lots of time off. (But it still kills me to pay $800 in fees for my "free" tickets when I can do better than that from Manchester!!)
You're going to have a great time! The kids will just be bowled over. A little jealous that you get to have that first experience with them. I remember our first trip with our two very fondly.
