*Sigh* Oh, you’re THAT kind of parent.
Look, the video games and iPad or whatever is not the problem. Speaking as someone who has ADHD and loves reading, video games, programming, etc while also hating things like sports, I can tell you that you can live a perfectly normal life without harsh restrictions. Also, don’t throw the word “addiction” around like you own it. Unless it’s diagnosed, it isn’t an addiction.
Instead of blaming the technology and forcing things down the kids’ throats like parental controls or sports, try motivating the kids. They probably realize that the “variable homework” is pretty useless or they don’t need to study. If their grades are slumping, it’s your fault, not their hobbies’. Try motivating them through positive reinforcement and limited rewards. Things like “good job on your test” or giving a quarter for doing their homework, things like that. Studies show that positivity works waaaaay better than punishment and negative reinforcement.