We often play wedding ceremonies where diddly is not appropriate ....blush , I mean, where one needs more sedate but not sedated music. Waltzes are nice and middle of the road. You can usually get away with hornpipes played at a reasonable speed. There is a whole body of work published by 18th century Scottish musician James Oswald that was "drawing room" type music, Neil Gow is another one, and as noted, O'Carolan. No need to get classical here.

We have recorded several CDs of instrumental music -"Tapestry" collection
You can hear some of our music at http://www.cdbaby.com/all/castlebay
Click on any of the Tapestry recordings
Most of the music is public domain

Good luck- I'm sure you will play lovely music and everyone will enjoy it
Best- Julia Lane