I believe my 12 year old is one of the rare kids that knows Splash Mountain was even based off a movie at all... and she's seen it (the movie) several times. Honestly, until I looked into the history of the ride, I had no idea either.
Thankfully I have a kid who takes rides as nothing more than rides. She knows they have a movie/story behind them, but doesn't think the ride/area is pointless if it doesn't pertain to current pop culture. She asked who Gadget was, and I explained that it was a cartoon from my youth (like Roger Rabbit, the story/record of it's a small world, Alice in Wonderland, and all the others she hadn't seen or known about), and she just took it at face value--cute theming and on to the next attraction.