Keeping the waist trim, will certainly make the shoulders appear wider too. Arnold used to make a point of his narrow shoulders, and compared to others BB'ers, he did have less shoulder width. (which can be rather genetic) His trim waist made him look quite wide. (then again maybe not a good person to compare our natural selves to.)
Nothing wrong with back work and some delt work. Personally, I feel heavy OH pressing does as much for building broad delts and thick shoulders as laterals. YMMV. Heavy DL's, rowing and chinning too.
Lastly, even if you make the area thicker, and not necessarily wider, you will still create the look of a weighty strong guy.