The most common ideas that spires to mind to do a social event that contribute to community is organizing a blood donation event or a clean-up event.
Last December I was in Dhiffushi, for holiday.
To my surprise in Dhiffushi there was a German NGO Ozeankind, conducting a campaign to help cleaning plastics. Along with the support from guesthouses in the Island they were planning a clean-up event.
I was able to interview the German who is leading the NGO.
Apparently, the idea of eradicating plastic from the ocean occurred to them while holiday in Maldives couple a years ago.
Since then they have held few clean up events in different islands alongside an awareness session.
You shall find their interview here.
https://www.youtube.com/watch?v=W-ngsknM8rY