When I am towing my pop-up, Sjm9911, 600 miles a day is my functional limit. Sometimes conditions will warrant an extra 100 miles but things really have to line up for that to work. That equates to about 9 hours from pull-out to pull-in including all stops.
Personally, I don't like towing into the evening after towing all day because by that time I am tired. So I plan my stops to arrive before dark.
Also depends on what cities I have to tow through. Going to WDW from Alabama, the only "big city" I have to drive through is Tallahassee and fortunately I-10 is about 5 lanes wide in each direction at that point. So unless there is a traffic accident or road construction, I just cruise along and eat up the miles. But when I tow north up I-65 towards my old home town in northeast Ohio, you're bound to run into trouble of some sort in one of the big cities: Nashville, Louisville, Cincinnati, Columbus. It's gonna be rush hour somewhere.
With my Aliner I can do the quick overnight stay and remain hitched up and drop the rear stabilizers then simply pop the roof and plug in. It literally takes less than 5 minutes. This is what I do at Lake Louisa SP the night before arriving at the Fort. The thing I have learned I don't like is to arrive later at the Fort (say 4-5pm), unhook and do the set-up, breath the Disney air and pay $150 for that night's privilege. So I like to arrive at the Fort before lunch time even if I have to wait.
If this is your first attempt at the drive, I think you should not bite off more than you can chew. So do the drive down in two days and arrive at the Fort on the morning of the third day after a short drive. Maybe home run it back home in two full days. It also depends on if you are travelling on a weekend day (less traffic in metros?) or weekday and may experience morning/evening commuting times.
Mechanically if you have the right tow vehicle that can handle your trailer, time on the engine is not the issue. Driver fatigue and passenger experience is more important. Do a little sight-seeing along the way ("look kids, the world's biggest ball of yarn"). Give your family a good experience travelling and they won't mind making future trips to WDW.
Bama Ed
PS - I do all the behind-the-wheel time so mine is a solo driving opinion. If you have someone to split the drive time, that helps.
PPS - be careful taking towing advice from Teamubr - he flies low-to-the-ground and has hundreds of hours in the cockpit. I hope to attain his level of experience in my remaining lifetime.