Oh how I envy the 1st timers.
For what it's worth, here's our must sees:
Illuminations: the fireworks show at Epcot's World Showcase, it's on every night at 9 pm.
A turkey leg and a dole whip while watching the Spectromagic parade and Wishes at Magic Kingdom. Camp out on main street or in front of the castle.
Eat at Crystal Palace at Magic Kingdom around noon on Sunday morning after riding Buzz Lightyear a dozen or so times, and before the huge crowds arrive.
Get to Disney's Hollywood studios early one day, and run to Toy Story Mania for fastpasses and jump in line right away. Then return with your fastpass when it's time for your second go-round. It's the hottest ride at Studios.
Do the same thing for Soarin' at Epcot.
Festival of the Lion King at Animal Kingdom is a must see for everyone.
Don't rush around too much. The details at Disney are wonderful. You can't do it all in one trip, so don't even try. Leave some things to be done for the next trip. At some point, ride the horse carriage or double decker bus up main street at Magic Kingdom. Have a snack or drink at one of the walk-ups at World Showcase and watch the people go by. Drink plenty of water and eat lots of fruit to stay healthy. Don't go crazy, and throw the agenda in the garbage if it's driving everyone nuts.
Don't worry about shopping for everyone, but if you must buy stuff, wait til it rains or you really need a break from the heat. Then have them send the packages to GF so you're not carrying them around all day.
Get up early to beat the crowds, then take a break if possible in the middle of the day for a nap or swim at the GF pool. Come back to the parks at night or late afternoon for the parades and fireworks.
I've never been to Blizzard Beach or Typhoon Lagoon because we usually go when it's colder. No advice on that.
Have a magical time, and report back upon returning.