One of the most common questions I get asked when people find out I homeschool our kids without using any sort of prepackaged curriculum is, "How do you know you're not going to skip something vital?"
I have two answers to this question.
The first is: What is vital? Do you, as an educated adult really remember the life cycle of the honeybee? Chances are you'll say no, but you know where to go find the information if you need it. Bingo. That's vital. A curiosity about the world around us and the ability to find the find the information they need are replacing the older model of filling children's heads with facts. For one thing there are simply too many facts. For another information is at our fingertips like never before.
The second, more practical answer is this: Curriculum Standards.
From time to time I do what other certified teachers do. I go hunt up a list of things my age-group of students need to know and make sure I'm not missing anything. A lot of things are covered by living a normal life. Holidays and traditions? No problem! Personal hygiene? Got it. Counting by fives? Oops, forgot that one. Note to self, next time we're playing counting games, remember to count by fives for a while.
It's not hard to give a child a well-rounded education in the playful context of everyday life. It's really quite amazing how children who watch an episode of Kipper where he builds an igloo are suddenly quite keen to learn how water turns into ice and a science experiment using a freezer can turn into homemade popsicles!