Good morning, and thanks for contacting CTB.
I want to refer you to Chapter 5: Choosing Strategies to Promote Community Health and Development. Please click on our Learn a Skill graphic near the top of the page, and then on Table of Contents. Chapter 5 presents an overview of community organization and advocacy. Also, please look over the list of other chapters and pick those that are most relevant to your effort.
You are up against powerful incentives to develop retail facilities, and it will be important that as many neighbors as possible speak up for either: (1) preservation of the existing park or at least its key facilities, or (2) Mitigation of the park's loss by having the developer create a replacement park nearby. All of that is a negotiation process, so it will be important to talk to local government, planning/zoning authorities, and the developer. I don't know in which nation you live. In the USA, developers have responsibilities to mitigate adverse environmental and social impacts. If that is also true in you nation, you have some leverage to bring to negotiation.
I hope thhis is helpful, and wish you and your neighbors success in this effort.
