I think
Whitney would be really hip and refreshing on a boy, actually. I don't think it's popular enough on a girl to be a huge issue. If it really worries you, you could always put it in the middle name slot, call him by his middle name at home, and let him have his macho, manly name to use at school. Blade-Cutter-Superman
Whitney... or something.
There was a male
Whitney (character) on the TV show Smallville. He was the quarterback and was dating the hottest girl in school, so I immediately think boy when I hear
Whitney.
I think Whit can be used on its own. Also, I greatly prefer
Whitney to Whitley. I'm just sick of -ley names in general.
Whitney KaiWhitney LucWhitney OliverWhitney StellanWhitney AlasdairWhitney BramWhitney PatrickWhitney MariusWhitney RiordanWhitney DeanWhitney MalcolmWhitney GrahamWhitney Drake