We've driven from Katy to WDW twice and we only stopped for 1 night. Both times we arrived late afternoon/early evening, but that was because we got caught in bad congestion near Baton Rouge (once an accident, the other construction). We also had 2 young kids, so we made frequent stops. Tallahassee is about the halfway point, so if you can make it past you'll have a shorter 2nd day drive. You'll also lose an hour around Pensacola or Tallahassee (I can't remember which) because of the time zone change.
On the way home, we once took the scenic route along the Gulf. We went through Gulfport and Biloxi. It was nice because it was different. Mobile is also nice to drive through, you can see where the cruise ships dock and you can see the USS Alabama. There's a lot of water around Mobile, so that gives you some new scenery.
We leave about 7 am and drive until 7 or 8 pm, depending on how the kids are doing. It's really not a bad drive, it seems to go by quickly.
If you really push it and can make it to Lake City, FL (where 10 and 75 meet), you can sleep in if you'd like because you'll have a nice, short drive on the 2nd day.
And, FYI, there aren't a lot of hotel choices between Pensacola and Tallahassee. We tried a few, but they weren't in the best areas and they made me nervous, so we continued on. We stopped once in Defuniak Springs, but that's about it. So, you'll need to make a decision when you get close, stop in Pensacola or push it to Tallahassee.
Some people like to make their hotel reservations in advance, but we never do because we like to get as far as we can. We don't like having to stop while the kids are doing well just because we have a reservation. Instead, we stop at a FL welcome center and pick up a discount book on FL hotels. They have coupons you can use for your hotel stay. Then, I get on my smartphone and look up hotel reviews on TripAdvisor to see which ones in the coupon book will be good to stay at.
Good luck and have fun!