An interesting insight on this in Freakonomics is that things we do with our children don't affect their long-term development as strongly as things we are.

Take the effort to make yourself whatever kind of person you want your kids to grow up to be, and they are more likely to grow up into that person.

For example reading 50 books to your toddler is good for short-term amusement followed by teaching your kids that "books are for kids" leading to a belief that they've outgrown "silly books". By contrast letting your toddler see you read what you like teaches your toddler that "books are for grownups" and your kid will naturally model their behavior on yours.

My personal attitude is that I want my children to grow up curious, inquisitive and self-motivated. Supplying external structure can't supply those traits, I have to model them instead.