The social event dinner will start at 19h at Saint John's College (Maps)
People meet at The Mill Pond, on / around the bridge to Laundress Green ( http://osm.org/go/0EQHc1cB6?m= ) and split into groups depending on what they want to do. Several options:
1) Go to a pub. There are several nearby overlooking the pond.
2) Hire a punt (Scudamores is right there: http://www.scudamores.com) and either go downriver and look at the backs of the colleges, or upriver towards Granchester (probably not all of the way to Granchester though, because they have to be back for dinner)
3) Walk to Granchester. Follow the riverside path and go to The Orchard ( http://osm.org/go/0EQHE5Gn?m= ) for a traditional English cream tea. Should be about an hour's walk in each direction, plus tea drinking time.
4) Go to one of the nearby museums: