I plan to level enh and still heal as well. It shouldnt be a problem, never has been for ret paladins or feral druids.
Staffs are even decent weapons for leveling when enhancement, because they give you some caster stats (which help for both enh/ele and healing), but still have slow attack speed/high damage per hit, which works well with windfury. Shamans are the only class that can benefit from both the melee damage and the caster stats on staves - take advantage of it.