My friend and I sang the song to someone who couldn't make the premier day, and we did it such that she basically took Rainbow Dash and Lix Spittle, while I took Captain Caelano, Mullet, and Boyle.
In depth:
While she sang the last "awesome" of the first verse, I entered with the "Ah, ah, ah~" and she joined back in for the "awesome" and continued through before I picked up Caelano's verse where we just dropped singing the backing because it was too hard, with the exception of the "It's time to be awesome" before/during "And now it's time" where she joined back in on "to break the shackles free" with her holding the "bold" out while I dropped out to pick up the "It's time to be awesome" with her joining back in on the "awesome."
We only practiced in-depth up to there because we kept messing up, but that's how we kept the gist of the song with only two people singing.
When we did our initial run-throughs of the whole song, she took the high pirate part (Lix Spittle) while I took the lows.
Just some comments; feel free to disregard.
Thanks for your time and work