When the activities for the participants or citizen scientists of your project have ended, and you as the initiator want to start analyzing the data or writing reports about it, it is important not to lose sight of the aftercare for your citizen scientists. Continue to communicate to them regularly about the different steps that are now being taken and how they work.
Don't forget to thank your citizen scientists for participating at the end of the project. For example, organize a closing event to which all citizen scientists are invited and to which they can contribute with a presentation. You can include the citizen scientists who contributed most to the project as co-authors on scientific or other publications or mention them in acknowledgments. Finally, you can also state the names of the citizen scientists (who have given their consent for this) on the project website.
Also make sure to keep the project's website online afterwards. Not only put the results and data of the project here, but also the methodology followed, important good practices that you have learned or things that went wrong and that you would do differently next time. This is valuable information for others who want to set up a similar project after you.