If you already teach html5 css then you dont need c2 ... unless u want to teach kids how to make games, and introduce them to Game development ... but then again it wont help them to much ... because you wont have native coding... all the code exported with C2 is scrambled (encoded) so you wont be able to read anything useful... if the class purpose is to teach web designing keep it as simple as possible which is html5 and css customization's ... the best and simplest way.. and you could also include some JavaScript usage with them...since they will need in future... all those can be easily learned or get info tutorials from w3schools.
if your looking for a simple Web design engine... i suggest teach the kids html5 ,css and some implementation of JavaScript and introduce them to WordPress ... then if they want to learn more they can take a programming language class (java ,python , c++,c# etc)
and if you do have kids as students , they will love to see that by writing some stuff in notepad... does internet stuff which is like lego for them and they all eventually love it
hope you understand have a great day!