Most of the discount ticket deals are for attending timeshares. Be careful buying them on Ebay, I got ours on there for our trip a few weeks ago but there were tons of scam listings to fish through before finding authentic ones.
I do recommend getting tickets with the water park option--the Disney water parks are a blast! If you do Animal Kingdom I would recommend going in the morning and being first in line to get on the safari ride. The line builds up FAST because the most of the animals are still out and visible while it's semi-cool in the morning. But other than the safari we didn't have too much fun there, in fact we left before noon and park-hopped back to Magic Kingdom. Your teenagers might like Disney MGM, it's got cool stuff like action shows and movie sets/props (Disney's version of Universal Studios). The city walk at Universal is kinda fun to go for dinner one night, lots of nice restaurants and shopping. I thought it was better than Downtown Disney.
I haven't done GatorLand, but my dad and his wife did and enjoyed it a lot, you go on a boat in the water and see real live gators I guess!
Have fun! Oh, just a tip: when we were there a few weeks ago we went back to some of the parks in the late afternoon/evening after our kids had taken naps. Getting there at that time was perfect for riding rides with no waits because TONS of people were leaving the parks for dinner!