Hi - I'm new to this board but I saw your post and I thought I'd offer my thoughts
I just did this drive over the holidays, driving down from Kanata on Dec 22 - we left at 3pm and even though I had a number of options, we made it to the preferred place which was south of Harrisburg on day 1. You really want to get as far as possible on day 1 because it makes day 2 easier. Plus everyone is excited on day 1 so the hours go by fast.
Anyways, here is a list of my suggestions based on mine experience and those of some friends who have been doing this from Ottawa down to Sunshine land over the years:
Load Navigator on your tablet and maps of each state and province you go through. That way your gps gives you a great nav system AND it shows miles per hour if you don't have them, and tells you if you are speeding. Basically free US nav system without any data plan needed! Great idea
Don't book any hotels in advance. You don't want to be tied down to getting anywhere. Each state has a visitor centre where you can get hotel booklets which give you rates for each - usually they will honour. Seems like you always get a better deal than online. And you can stop when you feel like it
Directions:
From Ottawa - don't cross at Ogdensburg! In winter the US side is dicey and in summer its full on Mennonite carriages. Country road. Instead, use the 401 on the Canadian side and cross at Thousand Islands. This is a big time saver
Empire State: Pick up the 81 and just get through NY State. Don't take the 481 ring road bypass at Syracuse - all the locals live on it so the 81 expresses you through the place much faster
Crossing into Pennsylvania, the KeyStone State, prepare for fog through Wilkes Barre area - can get very bad. No matter what time of year. If its winter, once you are through here you are generally clear of the bad weather!
Stay on 81 past Harrisburg. Now you are faced with the big 'Washington DC' question. Yes its true DC has tremendously heavy traffic and Maryland can be a bit daunting, especially if you are more used to Ottawa traffic. You don't want to go anywhere near the Baltimore-DC Beltway if you can avoid it (too bad all you Maritimers/Newfies that get struck here). DC traffic is really bad on the 95 south but it breaks up significantly around Fredericksburg so the key is to come through there.
There are 2 great options:
Stay on 81 until you pick up the i64 and come through Charlottesville and then on to the i95 at Richmond
or
My preferred: on 81 south of Winchester get the i66 over to Marshall where you pick up the #17 (which is the same as #15 for a stretch) which brings you out at Fredericksburg where you get the old i95. This is all twinned but watch your speed. Easy driving and saves 40min over the Charlottesville route.
Now take i95 to sunshine. Do take the 295 ring road bypass around Richmond - will normally save time
Stay on i95 through Jacksonville - the 295 bypass either way is where the locals live.
Also, the first tourist bureau in Florida - go in and get your free orange juice/grapefruit juice - nothing taste better and good washrooms there, maps and attraction brochures to keep kids entertained for the final leg
After that, I head to Miami so no so much help re drive to Orlando
Do get CAA - it becomes
AAA in US which is huge relief if you have problems and sometimes gets you extra discounts.
Canadian credit cards often don't work in US gas pumps since you need a zip code so make sure you have cash for gas and don't fill up too late.
Have fun! Its a great road trip - its cool when you first notice palm trees and when you ponder what they mean by 'American Cheese'