My kids never got bored over 4 days-only 1 was a teen. They swam in the pools and ocean. They also loved the water slides and lazy river. There were no teen activities scheduled for the time we were there in June during the week so we never experienced one. They were all scheduled on the weekend in June. We rented paddle boards and swam in their coral reef tank. There was just a lot for us to do. I would visit the Aulani board
I didn't travel with teens, but there were many teens when I was there and everyone (every age) was having a delightful time. Aulani is not all character meetings and toddler things. In fact, to me it is a luxe high end resort and once in a while you'll see Mickey. It's fantastic!
My teens were not bored at all! I have two teenagers(boy and girl) and we brought along two of their cousins(another boy and girl). Everyone has a different personality; some are more outgoing than the others and I felt like everyone found their niche.
The four of them did some of the scheduled teen game nights and scavenger hunts, but then also explored the area on their own. My son and nephew really enjoyed the ukulele class(sign up early because spots fill up fast) and my daughter and niece liked getting snacks and taking pictures with the characters. Everyone loved the pool area.
My daughter always says that the trip with her cousin was the most fun trip she has ever had, and my son keeps asking to go back so I think your teens will love it!