Regarding the Florida leg, I'd concur that the trip around I-275 through Tampa/St. Petersburg over the Sunshine Skyway is worthwhile and is a lot more interesting than staying on I-75 (unless you have a compelling reason like a clinch). I may go that way again next time I'm in the area just because I'm not satisfied with the pictures I took of the bridge the last time we went that way.
My relatives in Fort Myers and Miami have said that US-41 isn't worth the time, and my brother-in-law's wife feels it's not safe at night. With that said, last June we used a part of that road last summer to go from my brother-in-law's house (Pines Boulevard area in Pembroke Pines) to Shark Valley and I didn't think the construction mentioned above was much of an issue. It's possible the project has evolved since then, but he was driving and he was hauling along at 75+ mph at times. I will concur that there didn't seem to be a lot to see along the way if your goal is simply going from one place to another. I think I had a mental impression of the Everglades as being more like a bayou, which it definitely is not. But if you want to make some stops to see alligators or other wildlife, US-41 is much better than the Interstate. The Shark Valley tram tour was an interesting diversion and our (then-)8-year-old nephew loved seeing the alligators close up. Incidentally, whichever road you take (US-41 or I-75), if you're low on gas as you approach the Naples area, fill up then. I don't know if there's a station anywhere along US-41, but my brother-in-law realized he was low and turned around and went back to a station on Krome Avenue rather than risk driving out to Shark Valley with it reading low. I-75 has that gas station run by the Indians halfway across and everyone says it's expensive.
Disney World is not a realistic day trip from Miami unless you get up super-duper early and come back super-duper late; even then, you wouldn't be doing it justice. I mean, you could do it, but I don't think it would be a particularly worthwhile way to do it. The thing is, Disney is a huge resort. Don't think of "Disney World" as one amusement park, because it's not. The Magic Kingdom, EPCOT, the Animal Kingdom, and the others are all SEPARATE theme parks within the overall Disney World resort (which itself includes other things like golf courses and a motor-racing circuit). Two days there would allow you to see the Magic Kingdom and most of (but not likely all of) EPCOT, and the amount of walking at EPCOT in particular can be draining, making the drive back to Miami seem quite long. If you want a day trip from Miami, the Keys are far more realistic, even if you don't make it all the way down to Key West.
Another roadgeek possibility in Florida (again if you're not working on an I-95 clinch) is to take I-295/FL-9A around the east side of Jacksonville. You get to go over an interesting cable-stayed bridge, the Dames Point Bridge. People on this forum suggested it to me prior to my last trip south last December and I was glad they did. Even my wife liked the change of pace from I-95 (recognizing we had stopped for the night near the Jacksonville Airport, so we went over it first thing in the morning instead of at the tail end of a 700-mile day). I think on our next trip that way in June I'll go straight through Jacksonville to check off about a five-mile segment of I-95 I've somehow missed, but if you're not looking for a clinch and you don't plan to stop in Jacksonville, the eastern beltway is a nice detour after what you may well find to be a seemingly endless slog up from Miami.
On Day 15, be careful around Ridgeland, South Carolina. They've taken down their illegal speed camera but they're still a notorious speedtrap town for their roughly 7 miles of I-95. I went through there on a Saturday last July and they had six patrol cars on the shoulders pulling over drivers identified by a cop standing on a bridge with a radar gun and a handheld radio. The speed limit there is 70 mph and I think it's probably sensible just to slow down to between 65 and 70. I've noticed when I go through there that most people with South Carolina plates, and most truck drivers, all slow down and many move to the right lane to let the out-of-state suckers go flying past.
On Day 16, my brother says that Garrett County, Maryland (the first one after you cross over from West Virginia on I-68) is a notorious speedtrap. I've never seen a cop on there, but he says he's seen people who have been pulled over and the cops go overboard searching their cars and the like. I suspect the issue there is that my brother likes to travel to concerts and music festivals, usually Grateful Dead–related, and so I don't doubt that he's on that road on weekends when concert-goers are passing through and the cops all know this too.
