Do not begin. If you ask the question "how to begin" then you are not ready.
If you are forced to begin teaching, here are some ideas:
- for you: learn C++ well so that you can answer any question that children may ask.
http://www.cplusplus.com/doc/tutorial/
http://www.cplusplus.com/reference/
http://en.cppreference.com/w/
http://www.icce.rug.nl/documents/cplusplus/
http://www.parashift.com/c++-faq/
- explain to children that:
1) they write a text file .cpp that will be transformed into .exe
2) a C++ program has a special and unique function named
main() and that's where the program starts
3) variables hold information that can change
4) variables have more types:
int,
float,
double,
char depending on what information they hold
5) inside functions there are structures such as
if(),
for() and
while(), and explain what they do
If you do the above, you will teach the children the basics of the C language.
If you want to continue and teach C++, you need to explain the Object Oriented Programming (OOP) style, and teach them to use elements of the C++ Standard Library (STL).