We drove once from the DC area (so down I-95 most of the way, then you cut over I-4 I believe). But, it was right after the attack on September 11, so we were unsure of flying with our precious 2 and 4 year olds. (We had a trip that October booked, just the two of us, to Hawaii, but canceled that, and decided we didn't want to vacation away from our kids quite yet). This drive down was in mid-December, and we had just bought a terrific minivan (with a DVD player - our first, so I bought a bunch of Disney DVD's for the drive, which was super cool).
We stayed for 11 nights (of course got a great deal, since Disney was very quiet after the horrible attack) at the Boardwalk Villas. Then drove down to Naples to see my folks and then ALL THE WAY home (yuck) from south Florida.
The positive: we had a comfy minivan, brought our double stroller, all our groceries, snacks. bottles of water, etc... We never even needed to go to the grocery store - matter of fact, once we got settled into the villa, we never once used the van until we checked out. I loved having all our stuff (and I love road trips). We left after the kids got out of school (preschool, so it was about 11:00AM, picked up DH at work then just got on the way). Kept planning on stopping, but the kids were sound asleep by 8:00PM so just kept driving. Finally, stopped and stayed at a Downtown Disney hotel for the night (the Boardwalk didn't have a villa ready or it would be more $ or something so we wanted to save by staying somewhere cheaper, since we pulled in about 1:00AM and just needed a few hours of sleep). Also good was that (I think due to less people traveling) I-95 was not too terribly busy. It can be SUPER busy, like bumper to bumper for miles and miles. Trust me: I have driven to Williamsburg from here, and it should take 3 1/2 hours and it sometimes takes DOUBLE that with the darn I-95 traffic.
The negative: we were so tired next day, but the kids were up at 6:00AM. Still, we had lots of time, so took it slow and easy. Also - the drive HOME. Sucks. No way around it. It was LONG.
Now, you live way north of me. My cutoff for a road trip is 12 hours driving (I have driven to St. Louis to see family, but we normally fly, and I-70 west is no where near as bad as I-95). You're talking a LONG drive. LONG!
I think I'd definitely research flying and renting a car. You'd be there in just a few hours, and feel so much better than if you drove. You can get rental cars in Orlando at a decent rate, especially if you check early and often for good deals. I got a car for 15 nights last August for less than $250 taxes included - so the kids and I flew (and we got deals with Interval International getaways, so it was a good cheap long trip).
I just think that's a long long long drive, and that highway can be a bear through DC and just south of DC.