Kegging for real ale and bottling from same batch?

I have 5 gallons of ESB sitting in secondary in my kitchen. There is a Real Ale competition coming up next month in my homebrew club that I want to enter it in. The only problem is that I have no kegging equipment of my own. A homebrew club member is letting me borrow a corny keg, and the club has beer engines. Here is my question: I have no way to store it or enough people to drink 5 gallons of real ale that day or even that week; I would like to not waste it. Here is my question: can I keg half of the 5 gallons and bottle the other half? I heard you need to prime with different amounts of sugar if you are to bottle versus keg. Anyone have any suggestions or advice for me?

Thanks!!

Dan

Do you have a way to hit the keg with some co2 before you start any of this ?

What I have done in the past is prime in the keg, then bottle some once the beer is carbonated (biermuncher bottling method). You would need C02 to do this.