I think the idea of doing Seva is excellent and perhaps the true spirit in which Mother lived Her life. I was thinking more in terms of something here in the courtyard like Jayanti suggested. Maybe the initial incident that drew us towards the Mother or a quote which has the most meaning for us. Something more personal.
Namaste Pantosh, Mother's Courtyard is pleasantly 'awash' with touching mentions of her birthday. Even those of us, who are unable to leave their premises, due to various causes and/or circumstances; there are ways to volunteer from home, using the computer and the telephone. I totally agree with your comment of Seva, being the true spirit in which the Consort of Sri Sri Ramakrishna Parmahamsadeva lived her life.