An event that is actually helpful but also fun. Make everyone sit in a circle and whisper in each others ears 2 secrets (either heartfelt or interesting) that would be advisable for a good married life. Individual person write the secrets passed on to you in a paper and put it inside a box.

Later one of you can take all of them, open it and write it down on a decorated keepsake book and gift it to the dear bride on her wedding day.