Application for Video Game

I need Game Application for a Client and his requirements are follows :- What I need done: I need a video game program made from scratch. It should allow my son to select a game theme, and characters that can be customized. Then begin play the game with standard video game capabilities. It should not require advance reading skills beyond a kindergarten level. What I already have versus what the provider will build: This is a brand new application. I need a full design done, with modest graphics. The level of graphic sophistication is open to interpretation. It should include open source sounds, music and have the ability to be enhanced as my son grows older. Other context/requirements that providers will need to know: In terms of style, my son does enjoy games on his DS and XBOX but this application doesn’t need to look as realistic. It needs to be very simple, easy to use. The user interface must be highly intuitive and preferably drag-n-drop type of feature to build new games. This would allow my son to create a new game each time he opens it without understanding the backend programming. Specific expertise that I am seeking: You should have experience designing video games in one or more of the popular programming languages.