One example of designing for the family could be "Pooh's Honey Hunt" in Tokyo Disneyland. The ride had to be sophisticated enough to attract adults, but cute and childlike enough to work for the whole family. In Japan, the challenge was to attract "office ladies" that would invite a boy to take them to Disneyland. "Office ladies" usually live at home but are of college age or in their 20's and have disposable income. So the idea was to take the most sophisticated technology and special effects we had used elsewhere, combine them with a breakthrough ride system (wireless vehicles), and a hugely cute character. We took something that would be typically done with black light and plywood sets as a Fantasyland dark ride, and translated it into an "E ticket" scale megashow. This had not been done before. The repeatability of the ride due to its magical nature is kind of unparalleled as the wait times even with fast pass where many hours long and it was the most popular ride in the park for the least five years if not more. Usually new rides where off in 18 months, this did not happen with Pooh. Like a Big Thunder Mountain Railroad, a coaster that is neither too fast or too slow, but just right for the family becomes timeless. I think by going "all the way" with the technology and special effects in Winnie the Pooh we were able to create something that was magical for everyone. I don't believe that the other Winnie the Pooh rides achieved this level of repeatability and success. (they also didn't have the budget!) So in answer to your question, you can design on two levels, one, the simplicity of story for a child, and then sustain the magic in a very high level to entertain an adult. that's why I think Disney animated films have done so well over the years is that grown-ups sense the incredible level of execution given to a simple story and they appreciate it. That execution allows the spell of fantasy not to be broken no matter who is in the audience.
Here's a link to it.
http://www.tdrfan.com/tdl/fantasyland/poohs_hunny_hunt/index.htm
Thrill rides by nature are self editing as the intensity sorts out the age group of the guests. Theatrical show experiences are usually broader in nature. Big thunder hit the sweet spot of intensity. Teens outgrow it but families still love it. That I think is the real success of that show (because visually and creatively it's really not that original), is in its execution, as it has been done at such a high level it's a fantastic attraction.
I hope this answers your question.