If we were to get James White, we should trade down to get something extra (perhaps trade with Minnesota for the #36 and #37 picks) and take him there. Honestly, I can't see White getting into the first round when there are many talented, standout players (Lowry, Barea, Tucker, Freeland, etc.) still jockeying for position to get there.
If Phil emphasizes three point shooting coupled with athleticism, I agree with the fact that Shannon Brown and perhaps even Quincy Douby would be good choices there. It seems that many scouts, however, have lost some hope on Douby as his stock has been plummeting this past week (fell from mid-1st to late-1st). But either pick would be fine; Douby has a more diversified offensive game, whereas Brown has more polish within the team system. I tend to believe Brown would be a better fit here.
Guillermo Diaz would provide us with some athleticism, but as for three point shooting?...I'm iffy on that. I mean, he can certainly shoot and get hot from three point range, but he's not an overly reliable three point shooter; that's just a part of his offensive game. If we want three point shooting, there are better options than him.
Jordan Farmar has a streaky shot; not a three point shooter yet. But it's amazing how athletic he really is, I'll give you that. As for Ager, he's a slasher and a shooter who can get hot for spurts, but I won't exactly call him a three point shooter.
Shawne Williams, once he refines his skills, can potentially provide us with athleticism and three point shooting. He's only a 31% three point shooter but he has great potential to be good in this area. He's long, but his athleticism is not out of this world, but he's definitely serviceable for the NBA in that area. If Phil wants three point shooting, I think there are better alternatives than Williams at this stage. If he wants potential players with a good skill set, Williams would be a good guy to draft.
Another guy to consider for athleticism and three point shooting is Marcus "Marquinhos" Vinicius. His attributes are quite similar to Williams, however, as he's only a serviceable athlete and his three point shot can get a little streaky. However, he can be an all-around player once he makes use of his length and physical tools, as his skill set is already fairly decent. Phil seems to like him with the Triangle offense, but it seems like some scouts have lost some interest in him after a recent poor showing at Treviso. He's more of an all-around potential pick rather than a specialized three point shooter pick, however, so I don't think he's the best choice for that as well.
I think Shannon Brown would be the best pick for that.