I just want to say that not only is it possible to teach the basics of calculus to a very young child, I highly recommend it. At the very, very least an introduction to terminology and the basic ideas in a fun way that ensures the kid will grow up comfortable with it!
My hubby and I have both gone through all levels of calculus and beyond, and I assure you that much of what people struggle with in math ( as well as science!) is the language and terminology. It is very much like another language. If you are sitting in a classroom and the professor is using specific terminology to refer to the problem, and you don’t even know that vocabulary, you are not going to even begin to focus on the problem. Your brain begins to shut down at the onslaught of unfamiliar language:)
For example: using language from simple arithmetic, if you not familiar with the language, and someone has lots of numbers on the board…they are attempting to teach you saying things like the following. Okay, you first write the minuend like so. Directly underneath write the subtrahend, making sure to align the ones, tens, and hundreds columns. Finally, subtract to find the difference. Etc.
Anyway, we started teaching Alex the barest of bare bones at about 2. It began with making sure she could read a bar graph, and then other graphs. We made sure to always refer to the x-axis and the y-axis. Then using more pre-algebra terminology for things like a line : learning the formula (rote memorization then), what a slope was…that takes you nicely into. 'Change '. How to change the slope of the line and so forth, and introducing functions.
Once the child is more familiar with arithmetic, it be ones easier. Once Alex understood multiplication and division it becomes much easier, but it isn’t strictly necessary to develop understanding. If you have access to a decent graphing calculator or graphing program, it is easy to enthrall them with possibilities, but again, not totally necessary.
I do have the Introductory Calculus for Infants book as well as the others in the series, and we do those at night. We read at least one ‘living math’ book as part of our bedtime reading, and this is a great time for those. For more of a system /fun supplement to our daily math we use Calculus by and for Young People book and worksheets and Calculus Without Tears. I will say that these both have a very homespun feel to them, completely different to the style of the cute series of math books. But they are great resources for a parent wanting to teach to a child.
http://www.amazon.com/Calculus-Young-People-Ages-Yes/dp/096216741X/ref=sr_1_2?s=books&ie=UTF8&qid=1373052869&sr=1-2&keywords=calculus+by+and+for+young+people
http://www.amazon.com/Calculus-Without-Tears-Learning-Students/dp/0976413809/ref=pd_sim_sbs_b_4
Edit: BTW, the author of Calculus by and for Young People, Donald Cohen, has a website with LOTS of great ideas for calculus and more advanced math topics. I referenced it in previous threads, but it has been awhile, so here it is again:
http://www.mathman.biz/