Let me chuck my 2 cents in as a goofy runner last year. Advice from my own experience and what my advice would have been based on others experiences (or lack of them)
1. It was bloody cold last year, it was basically a state emergency, quite funny to us but as they do not get such cold temps (talking -2 here) they are not prepared. There are no gritters, pipes freeze, tropical fish farms all the fish die. It was cold at the start and stayed so for the whole race both days, it was cold our whole stay except the first day. So take warm clothes to run in, I didn't do it massively and was runninn in shorts and all 3 running tops they gave me, you couldn't buy a pair of gloves anywhere and I ran in some designed for cleaning. It might be warmer this year, tbh we're obviously a bit more used to cold weather than they are, some people were running in winter coats.
2. Flight Delays - My advice is to make sure that your marathon is one of the last things you do on your holiday. I flew Dec 30th and flew back on the 13th Jan. I had a few days after the race but about 10 days before them. Quite a few people on this forum last year flew out a few days before the race or tried to. Snow delays in the UK meant that they missed the race, with all the preparation and cost involved its not worth the risk IMO.
3. Places to stay - we stayed on I-Drive in a cheap hotel near Universal and rented a car. We walked to Universal when we went there and drove everywhere else. It worked well for us, it works out a lot cheaper than staying at Disney, our hotel was cheaper (and perfectly alright) and we were also able to take advantage of a variety of cheaper restaurants on I-Drive compared to Disney. Also if you stay at Disney, the transport isn;t there to take you to Universal and Seaworld, but it is to take you to Disney from I-Drive. It all depends on your budget and what you want to do.
4. Race Day - I think I got up at 4.30 and drove to the race, there were not many delays in getting parked and parking was free. It was a short walk to the event and then a longer walk to the actual start (i was not prepared for this)
5. Race Retreat - I didn't bother and it fell into the more money than sense camp for me. However if you were staying at Disney the buses left stupidly early and you would have stood around for a long time in the snow without it. I stayed in bed until 4.30, could eat a bagel whilst laying in bed, got dressed, drove there, sat in my warm car until time and gone straight to the start.
It was by far my favourite race of all time and considering it was the goofy and the hardest challenge I have ever done, it is also the only one I would consider doing again and look back with any fondness, not sure I said that as I was staggering around at mile 20 but it really was a nice event. I'd love to go back and do it again, even just to go back to orlando cos I love it.