Depends on which era of the Our Gang we're talking about.
The earlier silent era kids probably would have thought the Mouseketeers were sissies and beaten them up. The '40s MGM era Gang would have viewed the Mouseketeers as heroes. The Mousketeers would then proceed to wipe the Gang away in a talent show.
Another thing to keep in mind is that Walt Disney would have never allowed his kids to fight; Hal Roach would have.
And Louis B. Mayer? He'd only think it was okay to fight if the Mouseketeers were on Hitler's side. Or if everyone learned a valuable lesson in the end about friendship or some other nonsense.
Buckwheat Thomas was said to have been into drumming. Maybe he and Cubby could have had a drumming competition.
Alfalfa and Dennis Day would then have a sing-off. Neither could really sing, but Roach knows that his is part of Alfalfa's charm, and uses it to his advantage. Disney mistakenly thinks that Dennis Day is related to the other Dennis Day from THE JACK BENNY PROGRAM, and is hugely disappointed at the result.
The big climax would be a face-off between Annette and Darla. Darla would blow Annette away in the singing, but Annette would probably win in dancing. The tie is forced to be broken by Spanky, but being a woman hater, he takes the prize for himself.