Greetings. 

Project is only available as a separate license.  Once licensed the application is accessible through https://office.com.  Historically we have not seen very successful initiatives with this software. As a result, we steer people towards the Planner app that is included in our Office 365 license.  It allows for the management of projects but does not go as far as the full Project software.   I understand that you have been using Planner and still find it limiting.  Some find the browser version of planner to be easier to work with and get a more complete picture of all of their projects/tasks.  (https://tasks.office.com)  If you feel it is important to have all of the functionality of Project licenses for your team, Compare project management solutions and costs (It is important to note that the Project client can not be installed directly on a Mac so the differentiator between the plans should not really be considered when selecting the client for your team members with Mac devices.) 

If you would like to move forward with this solution, please send a reply with the preferred plan and names of those who should receive the license.  Our Microsoft 365 bill is processed on an annual basis in March.  Once the plan and numbers are settled, we will calculate the cost for the balance of this year and bill your department.

Let me know how you would like to proceed.  Thanks