Once again, I will give a non-standard reply.
Don't work too hard at making the TV kid proof. Just keeping the remotes and components out of reach and plan your system to be adaptable to changing needs.
Your son my be young now, but by age 4 he will know how to operate your system better than you will. If you work too hard to make it inaccessible, he will simply work harder to get there. IMO it is better to risk a $70 BluRay player tray than to walk into the room and see how he has piled chairs and boxes to get up to the one you placed out of reach.
If you have issues with the gaming systems, then purchase a cheap DVD player for his needs and put it in reach. Be aware that at some point games are going to be attractive, especially if you give in to the temptation of buying a few kid friendly ones.