Hello! I am mathematician and a homeschooler (that is - my children are homeschooled). If you want to capture the joy of mathematics, or the joy of anything for that matter, then it is my personal belief that the best curriculum is no curriculum. That last sentence is a bit of an exaggeration, but still my experience has shown that the most important things children discover themselves, and the most joyful moments of discovery are when one discovers something for oneself. Since you emphasize joy in your question, this is my answer.