Employee engagement is essential during planning phase and throughout the project. It provides a sense of directions and purpose, ownership, milestone achievement and etc. Do not over promises because it penetrates change fatigue due to overwork. There should be more of "WE" and less of "I" & "ME". This creates a dynamic project team. We are all in together - success or failure. Project Manager needs to provide some motivation factors i.e., say "thank you for the job well done", have lunch together, meet and discuss what went well or not so well, etc. These are some ideas. Bottom line, put yourself in their shoes. How would you like the Project Manager to treat you? I think that you will have a lot of answers. All the best.