Ok, so last year I struggled with PF for 6 months before going to dr. You know, too busy to take care of it

Well, anyway, I went to my podiatrist and she was SOMEWHAT helpful. She said to wear ONLY sneakers (which I did already), do some stretching excersizes, and rest my foot. After that didn't help, she gave me a shot of cortizone in mid-summer (WDW trip in Sept). Well, that was WONDERFUL, but it only lasted about 3 weeks or so. I figured, no problem, just get another one right before the trip. Well, guess what - the second one did NOTHING. My podiatrist had said that this happens - it's less effective with each additional shot. She basically said that this was something I would have to live with and actually even talked surgery with me.
Well, I finnally brought it up with my chiropractor (I had been a very recent convert to the wonderfull aspects of a chiropractor). Well, he went to work right away. He said that the cortizone shot is a terrible shot - it breaks up the inflammation because it is a jagged little compound and it literally "tears" up the inflammation. (that's why it hurts so much if they don't numb the area first). Ok, the chiropractor "massaged" the heel with a "drill" - hurt like the dickens, but it would feel GREAT afterwards (no inflammation - no pain). He taught me some really good stretches and it started to feel better - not good, but better. Rolling the arch on a can is good, but a frozen bottle of water is what he recommended and gave me the most relief. Definitely had to ice the heel at night and vigoruosly stretch FIRST thing in the morning BEFORE getting out of bed. Oh, something to ask your doctor about - I didn't just stretch the heel, I needed to stretch my calf muscle, too. My chiropractor also had some sort of deep heat ultrasonic "thing", it would make my heel feel good, but only for a day or so.
I have to admit, at first I was pretty inconsistent with the stretches, but by the "end" I did them even a bit more than directed.
So besides being treated by the chiropractor, I found something else that helped. I got a pair of these inserts:
www.heel-that-pain.com
They didn't cure it 100%, but after wearing them for a few days to get used to them, they really did cut the pain in about half for me.
The last and BEST thing I did was to excersize on a "gazelle". I know it sounds crazy, but we got one to just get some excersize and it worked like a miracle. I would wear sneakers with my "heelthatpain" inserts and work out on the gazelle. At first, I could only do about 5 minutes because my feet would become sore, but after about 2 weeks, I suddenly realized that my heel didn't hurt AT ALL!!!!! And it has stayed that way. I think the gazelle allowed my heel to be stretch and also built up the muscle in my arch, but I'm just guessing at that.
Anyway, the last two summers I played softball in pain - could barely walk after resting 5 minutes. Could NEVER walk barefoot in our house - we have hardwood floors. And was constantly "limping" every evening or after resting my foot. Oh yeah, NO sandles or flipflos for me - NO WAY. I battled this for about 2 years in total. This summer - NO PAIN AT ALL. It's WONDERFUL. I can wear ANY shoe (but still wear my sneaker and inserts 75% of the time) and can even go barefoot!!!
IMHO:
For your WDW trip, see your dr. for some stretching excersizes ASAP and DO THEM!!!! Don't forget to ask about the calf muscle, too. Check into supports, either "custom" ones, "heel that pain" ones, or something else you find. Ice the heel EVERY night before bed and stretch before heading to the parks and after any type of rest. Wear sneakers ONLY - sorry

Oh, something else you can try for your trip, ask your dr. about "taping" your arch - I found something on-line after doing a google search and taped my arch before softball tournaments - it helped somewhat, too. My chiropractor also had taped my foot RIGHT before our trip last year.
WOW - I'm sorry this is so long - it's a subject near to my heart - I really FEEL for you!!!! Sending some pixie dust your way!!!!!