For us, unschooling does not mean kids doing only what they want all day long. IMO, real life means sometimes doing things you don't want to do. For my kids, that may be washing the dishes by hand, cleaning up after the dog, cleaning the bathroom and so on. We have several dogs and raise puppies. DD (16) does not like cleaning up after them but we pay her to look after them and she does a reasonable job. She would much rather be on the computer all day long but she has to share that and make time for her other chores around the farm, some of which she loves, like taking care of and working with her horses. Animals and chores are a wonderful way to show children that not everything necessary in life is fun.
She is "in" to rabbits so that is what she primarily studies on the computer, doing research on breeds, being involved with the local, state and national club and several chat forums. We have traveled several hours and spent all day for her to show her rabbits. Boring as all get out for me but thrilling for her. Most of the kids who show rabbits in our state are homeschooled so we run into many of the same people over and over again. For us, it was her finding a love and then us encouraging her to learn about it, get involved with it and us enabling that.
At 17, your ds should have some plans for the near future. If you went to college, you had to have had a plan, even if it went no farther into the future than planning to fill out the application and go to classes the next semester. He does not need to have his life planned out but what is he going to do to support himself at 18 or if you are going to support him, what is he going to be doing to learn to support himself in the near future (i.e. trade school, apprentice, community college)? Part of unschooling is about freedom right? Eventually you are going to have to make it clear that he is free to make his own way in the world - how is he going to do that?
Does he have a drivers license? If he is not working around the house on a daily basis, honestly, I would require some type of part time job to pay for his video games and players, not to mention snack food and other extras.
Did you know that gaming really is addictive? I have read that the pleasure spot that it stimulates in the brain is the same place that drugs stimulate. If your sons are addicted to gaming, they are going to constantly want that chemical rush their body produces. You might do a bit of research and see what other types of activities produce a rush so they are not constantly looking for it on the screen.http://hubpages.com/hub/IVideo-game-...-Does-it-exist
Don't get me wrong - my kids have a wii, I played as a kid and let mine. But we are careful about it and have a lot of learning games rather than just fast action. For instance, ds right now has a game where he is building another "world" creating characters, will build castles, lay out topography and so on.
You said "I'm trying to let my kids make their choices without letting those choices be a reflection on me. If they fail or succeed, doesn't it have more to do with what they've done rather than what I have or have not done as a parent?" I only agree with this to a certain extent. True, adult children that have been out of the home, make their own choices and if these are bad choices, the parents are not to blame. But, if they are good choices, do you not think that reflects on the parent? So why not the bad choices? The parents are not to blame but people will always wonder who did have a negative influence on that person as a child. Kids that are still at home, living with parents that are able to guide them, instill morals, beliefs, encourage a work ethic, for sure their choices reflect on mom or dad. Does not necessarily mean mom or dad is to blame for bad choices.
Sorry to post such a long reply. It is late, we have all been sick and the more tired I am the more "long-winded" I get in my typing. Hope I don't read this tomorrow and realize my medication is making me sound funny.