B.C.
I made my first trip to Disney land when I was 6 (1957) and I've been a Disney fan since Walt Disney's Wonderful word of Color came on TV in Black and White.
I would go and spend my time at Disney, except for one day at Universal Studios. My wife and I love Epcot, but we also had a wonderful time at the Animal Kingdom. We only spent one day at the Animal Kingdom and left for Epcot before the Animal Kingdom Park closed.
One of the things we did with our kids was to give them watches and set a time to meet them back at a certain place at a certain time for lunch and dinner. We had 8 kids and they got along well so we paired the older ones up and turned them loose. We had fun. They had fun. The older two took the youngest two with them until noon. Then they were off on their own with a brother or sister. At 14 and 17 they should do fine going off by themselves.
If you like gardening, be sure to go on the "Behind the Scenes" gardening tour at Epcot. It was fascinating. It often sells out for a day or two in advance. Book a date and time as soon as you get there.
We went to Universal studios to attend their luau. It was wonderful. It was even better than the luaus(several) we went to in Hawaii. I would recommend you do the luau if at all possible.
Hope you have lots of fun. Good luck to you and yours.