Kale, spinich, calcium and iron?

I recently went vegan, again, and I want to make sure I get enough calcium and iron without supplements. I bought a juicer and was starting every morning off with a mixture of veggies including spinich and Kale. I have been including a lemon for flavor and it's supposed to help iron absorbtion. I recently read, however, something about mixing kale and spinich and how they can counter act each other? Is this true and any other suggestions for gettin calcium and iron?