The humidity can be crazy before the sun comes up, and as soon as the sun does come up (which wont happen in the 5km and 10km!), the humidity drops but the temperature rises. The 2014 half marathon was the most uncomfortable conditions I've ever run in. Dripping in sweat within a mile of the start!
I've done this twice, and all rules regarding pacing and training go right out the window for me. Technically, you COULD race them all, but why would you want to? The Disney races are all about the experience, so if you fly around at your normal racing pace, I promise you'll miss out on a lot of what makes these races what they are. Character stops, theme park photo opportunities, on-course entertainment.. just take it easy and enjoy the atmosphere.
Not sure if its advised, but in the training, I'd stick to my normal marathon plan, but split my LSRs into two parts on the same day, so do 10 miles in the morning, have lunch, and hours rest, then 8-10 in the afternoon/evening.
As far as tactics go for the races, I always try to get to the start line of the marathon in the best possible shape. The 5km and 10km can be busy in places, so we slow the pace down, try not to dodge around people and waste energy, have a short walk in Epcot, take in the surroundings, get a few photos, and try to take as little out of our legs as possible.
The half marathon we usually slow the pace down again, have a brief walk in the theme parks, take a few photos when the opportunities arise, and try to finish feeling reasonably fresh (easier said than done in that humidity).
Then for the marathon, use whatever you have left. Usually start to struggle around ESPN Wide World of Sports, and adopt a run walk strategy from there. It's not nice to start a marathon feeling leggy, and if you get those first 3 races wrong, the Sunday could become a very long and painful day!
I have stayed on International Drive, but not whilst doing the Dopey. Ive never considered staying off-site during the races. I think at the very least, I would stay at a Disney resort for the nights before the half marathon and marathon, and then also the following night. I really cannot emphasise enough the convenience of the transportation between the Disney resorts and the event village, and then to the cooldown party in Disney Springs on the evening after the marathon. Its just one less thing to have to worry about.
Traffic getting into Epcot is usually very heavy on races mornings, but the buses bypass all of that. They also run non-stop, so you never have to wait more than a few minutes to board one. Then you have to decide if you'd want to drive after the marathon, considering you would've done 5km, 10km and 21km in the days leading up to it. Personally, I have enough trouble just walking after all that!!
Stay in one of the "value resorts". All-Stars Sports, Music & Movies, and Pop Century are all Disney resorts which come with the free transportation bells and whistles, and are a fraction of the price of the other more popular resorts. Having stayed in a few of them, I can guarantee that there's absolutely nothing wrong with them!!