I'M YOURS - Jason Mraz - Ukulele Tutorial | Chords | Lyrics @TeacherBob

You could have transposed down 4 semi tones to the Key of G and then use a Capo on the 4th fret using these easy chords; G D Em C and A7.

Lowering the tuning for all the strings is fine if you're only playing 1 song and not playing in a band. This is not proferred. Capo on 4 fret playing G Key Chords or play the B Key Chords barred.