There are no answer imo. If you or you're team know PHP - PHP is the best in this case. You will spend lots of time to learn and then do something with new language.
Show them something. Build something with your knowledge and show them to prove that you're not spending time. Build some educational website or something like this, then you're parents will be able to see that you're actually doing something when you 'spend' time with computer.
Grades are the way for your parents to see that you're good at school, if you build something with computer that would be the way for them to see that you're not spending time.
+1 for asana. But don't try to start searching for "best task management tool" or something like that. you will waste your time. Choose any tool, start using, if it fits your needs then stick with it.
Friendly reminder: launch iOS/Android version before someone else does