Select only direct children from element with Sass

Try this:

    ...
    & > div {width: 33%;}

    div {
      float: left;
      height: 4.1rem;
      line-height: 4.1rem;
      color: #fff;
      ...

Take out div width and apply it only on direct children. Leave rest as is.
Here is quick fiddle (remove .option and .search styles later, its only for visualisation).

Please edit your question and better explain what exactly you want to achieve.