My 14-year-old brother isn't growing his hair long (yet  ), but he likes to keep it longer & kinda shaggy. The problem is, it's just long enough that it hangs into his eyes, gets caught under his glasses, and sticks up over his ears. My stepmom keeps nagging him to get it cut, but he likes the length, and they both think that if he trims it he'll end up with one of those early-90's bowl cuts.

His hair is blond, straight, and kinda thin, with no body or wave. Does anyone have any suggestions on what he could do to neaten it up a bit?

I would suggest just trimming the front hair that gets in his eyes. If you cut it for him, you can cut with the scissors pointing INTO the hair, which will thin out his fringe area a bit. It might be easier for him to deal with his longer hair then.