The mayor and city council may, in their discretion, include all the real estate to be charged and assessed with the cost of such improvements in the improvement districts described in sections 16-617 to 16-635 but are not required to do so. The mayor and city council may, in their discretion, in determining whether the requisite majority of owners who are authorized in sections 16-617 to 16-635 to petition for improvements, and to object to the improvements and to determine the kind of material to be used therefor, have joined in such petition, determination, or objections, consider and take into account all the owners of real estate to be charged and assessed with the cost of any of such improvements, or only such as own lots, parts of lots, and real estate which, in fact, abut upon the part of the street, avenue, or alley proposed to be so improved. This section, in regard to the depth to which real estate may be charged and assessed, shall apply to all special taxes that may be levied by the mayor and city council in any such city in proportion to the front footage.