I didn't think there were any special lyrics to this song. Kubrick just closes with the Mickey Mouse Club song because it was a reflection of the times.
"Who's the leader of the club
That's made for you and me
M-I-C-K-E-Y M-O-U-S-E
Hey! there, Hi! there, Ho! there
You're as welcome as can be
M-I-C-K-E-Y M-O-U-S-E
Mickey Mouse!
Mickey Mouse!
Forever let us hold our banner
High! High! High! High!
Come along and sing a song
And join the jamboree!
M-I-C-K-E-Y M-O-U-S-E
Mickey Mouse club
We'll have fun
We'll be new faces
High! High! High! High!
We'll do things and
We'll go places
All around the world
We'll go marching
Who's the leader of the club
That's made for you and me
M-I-C-K-E-Y M-O-U-S-E
Hey! there, Hi! there, Ho! there
You're as welcome as can be
M-I-C-K-E-Y M-O-U-S-E
Mickey Mouse!
Mickey Mouse!
Forever let us hold our banner
High! High! High! High!
Come along and sing a song
And join the jamboree!
M-I-C-K-E-Y M-O-U-S-E"
It was a time when the average age of the American soldier was 19 y/o I believe, compared to 25 or 26 of WWII for example. We were kids fighting the kids of Vietnam.
The words "Who's the leader of the club..." certainly reflected the political uncertainty back home too. At least that's what I think he was trying to say with that closing song. Maybe I'm wrong?