Unless you plan to use the EWI as an additional voice for doubling, I would vote w/o hesitation for learning basic keyboard. You will need to put some time but it will slowly come and it will make you a far better musician. You don't need to be a proficient pianist just learn simple chords. On the Lt hand emphasize on the Root 3rd and 7th or 5th 3rd and 7th. Voice lead from chord to chord accordingly. Melody on the Rt hand. If you want, w/ the Rt hand free fingers you could add a voice extension but that is not necessary as the melody should evoke these.