We're writing a book on how to have powerful learning experiences without using curriculum, but in truth the approach is very simple:
Learning should be fun.
Children learn more quickly and the learning is more memorable when it's fun. Our hopes are that by introducing topics through fun activities, we will spark an interest in the learners.
Once curiosity is sparked, who knows where it'll lead? Let your children explore the topic on their own and within their own intelligences and learning styles. Let them choose how they will “play” with the information. Will they spend a couple hours Googling about it? Will they make posters? Write plays? Can you think of some ways your child would enjoy playing with the topic? Allow them to delve into the topics.
Don't be surprised when your children get all excited about the stuff they're learning. Don't be surprised when one interest expands into other interests. Don't be surprised when they become insatiable learners.
Just be happy you get to be part of the process! They are your wonderful children!