i play this on guitar, the actual one in the recording, but playing it on the uke i added some chunks in there and a new more upbeat rhythm and it is fun to play that way too. thanks for bringing that to my attention.
Adding a capo changes the key that the song is played in. If your Uke is tuned GCEA then capo 4 brings it into the key of E. If you want to make it sound like the original recording then use a capo but if you want to be able to sing to it (depending on your vocal range) then don't use a capo or capo it on a different fret.