Plus, I have made it a mission to consume as much of his beer as possible when I am at one of their parties. So, I'd like to just give him a ready to use keg with my Hog Mountain Logo plastered on it of course. .
I would suggest buying a sanke d coupler to force carb the kegs. Trying to fill an open keg with carbed beer could get ugly real fast if it starts foaming. Also, you will not have an ability to sample the amount of carbonation left in the finished beer. The $30 for a sanke coupler could save a bunch of heartache and your good reputation as a brewer!
Plus the extra work of transferring the beer from keg to keg to save a couple bucks....Sanke couplers hold their value, so in theory you could sell it someday for very little net cost!