First, make the game. Then, make your game playable on a computer platform.

Do not make the technical decisions until you first understand the reasons why they need to be made.

Is the goal of this exercise to have a completed video game as the end result, or to have a child motivated to learn how to make such games? If the latter, it may be prudent to build up to the final product, by starting with "Hello World", implementing command-line interface "Tic-Tac-Toe" or "Hunt the Wumpus", moving on to a 2-D falling tetromino game, doing a simple 3-D demo, and so on.

But either way, the initial focus should be on making a fun game, and the details of the execution subordinate at all times to the question "Does this make it more fun to play?"