Congrats on your upcoming trip!
So, first thing I'll ask is, are your teens into thrill rides?
-If so, make sure to make Fastpass+ reservations. Last time you were there they were still on the paper Fastpass system. Now, you can reserve your Fastpasses online ahead of your trip (and I highly recommend you do so since they fill up!) Since you'll be offsite for the majority of your trip, you can book them 30 days before your trip. (You might be able to book your very first day's Fastpass at 60 days before since you'll be at the campground your first night, I'm not sure, but i'm sure someone else will know!) You can make 3 Fastpass+ reservations per day, and then you can make an additional ones after you've arrived and have used them up. Edited to add: Make sure you have your park tickets purchased at least 30 days before your trip if you want to do this, since you'll need them to make Fastpasses!
If your kids are into thrills, I recommend Fastpass+ for:
Magic Kingdom: Space Mountain, Splash Mountain, Thunder Mountain
EPCOT: Test Track, Mission Space, Spaceship Earth (Although if you think your teens would have any interest whatsoever in seeing the new Frozen ride, I'd prioritize that ahead of anything and everything else!)
Hollywood Studios: Rockin Rollercoaster, Star Tours, and Tower of Terror
Animal Kingdom: Flight of Passage, Kilamanjaro Safari, Expedition Everest
Another thing that might be different since your last trip is dining. Now, it is almost essential to book any sit down restaurant you know you want to eat at 180 days in advance (so about six months). For you, that's next month! So I'd start researching now and book early in the morning at exactly 180 days- I think you can begin booking at 7AM EST (someone may correct me though, things are constantly changing!). Don't panic if you don't get a reservation the first day you try. Spots open up, and people can and do cancel right up until the day of the reservation- just keep checking back! : )
Finally, Downtown Disney is now Disney springs, and with teens, you'll definitely want to check it out! It's been renovated and completely expanded- it's fantastic!
Have a GREAT trip! My parents took me to Walt Disney World twice as a teen (and once to
Disneyland too as a bonus!) and I had an amazing time each time- it's a whole new experience!