I actually like this, mostly because of the nickname Whit, which is adorable. I'd say go for it. I think it's fine with Mustard too.
Never been that much of a fan of Walt/Walter, but Whitman is a bit more my style.
http://www.behindthename.com/pnl/72895
"It is human nature to think wisely and act in an absurd fashion." ~
Anatole France