Maybe think of the trip differently. Rather than a "we have to do lots of Disney trip", why not think and plan it as a fun journey of the southeast?
If it were me, I'd do the Milwaukee to Atlanta portion as one long day (saves you the hotel cost). I'd plan to leave at 6am from Milwaukee and get in about 9pm-10pm in Atlanta (Mapquest says it's 12-13 hours, but I'd bet with a nice stop for lunch and dinner, you're looking at 15 hours). You'd pretty much put the kids to bed and spend some time chatting with friends and then I'd spend Sun and maybe Monday exploring Atlanta (depending how much your friends would mind you hanging around). You could see the World Of Coke, Centennial Olympic Park, Center for the Puppetry Arts,
Legoland Discovery Center, CNN Studio Tour, etc. Then, I'd be up 1st thing Tuesday and get to Orlando by about 4pm for a hotel check in (if you leave by 8am, this should be pretty easy) and then you could spend an evening relaxing at a Disney site. I'd spend 2-3 days in Orlando and then the 2 days on the beach in Florida (as you mentioned) and then I'd turn around and drive to Nashville, TN and then home (possibly spending another day enjoying that site). So, my trip would be...
Day 1 - Drive from Milwaukee to Atlanta (longest drive time of the trip, but the 1st day, so you guys should be well-rested and excited, so this is the best way to do this)
Day 2-3 (3rd day is optional to enjoy more Atlanta - could swap with extra Nashville time) - Enjoy Atlanta
Day 4 - Drive from Atlanta to Orlando - enjoy evening activity
Day 5-7 - Enjoy Orlando
Day 8-9 - Enjoy Beach
Day 10 - Drive from Florida to Nashville
Day 11 - Optional Day for Nashville (if you didn't use the day previously) and/or drive home
I much prefer having whole days for exploring places than partial days when I roadtrip. I'm doing a full day on our travel to Florida to see Charleston, SC, so we can actually enjoy the day well-rested and ready to take it all in.