a big kahuna
The most important or powerful person in a group, organization, business, or movement (e.g., the boss, leader, etc.). Primarily heard in US, South Africa. I think it sounds like a great idea, but you'll have to ask the big kahuna first.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
a big kahunaor
a grand kahunaAMERICAN, INFORMAL
A big kahuna is a very important person in an organization. Suncorp Metway big kahuna Steve Jones may be thinking twice about his plans to start a business in North Queensland. Note: The word `kahuna' is from Hawaiian and means `wise man'.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012