Nice of you to put such specific consideration into their needs! I would think that timber blinds or white timber blinds (venetians, which are much cheaper than shutters, but can look just as good. Because they are easy to clean, but mostly because teens tend to hide out in their room, sometimes this turns into a cave and they don't really care about opening the blinds each morning, also, they are particularly concerned about their privacy and sense of space, having blinds means they won't ever look messy and the most you have to do is open them up, and if they are tilted a Articular way, they still provide them a private blockout while letting the directional light in. I would also do a timber floor for a both, as they are likely to traipse in wearing shoes that of course are full of stuff from their adventures. They play sports, may spend time outdoors and timber floors scan be easily cleaned, carpets are ruined. As for a girl, if she has different interests, or spends time in her room often, a carpet rug on a timber floor. Rugs can personalize a space, so they have some saying the decor, and easily replaced, maintaining your timber floors beneath, while providing warmth and comfort. Even if covered mostly by furniture, the edge of a rug underfoot will feel more comfortable than not.

Wow winner to me is the colour changing LED lighting, sets the mood for whatever you are doing: games, studying etc

I would you for neutral walls and floor and add colour with accessories and toys. This means that the decor can be easily changed as they get older. Perhaps shelves to dispays their treasures, or decorate with some of their own artworks.

He is a talented young man, sounds like he is a budding young designer, I think a black lamp would look very stylish, a patterned rug under bed could blend beautifully with his bedding, a warm throw blanket, an artwork either purchased or created by himself and an architectural plant and planter could just set off the room, lovely to see him so interested in helping to design his space.