Thanksgiving
I remember an NPR segment that suggested you could spend some time on Thanksgiving teaching your dinner guests about technology, such as how to use various features of smartphones, instead of fighting over politics. I say do both, though with less emphasis on fighting and more on learning and understanding social issues.
Thanksgiving's original purpose was to celebrate the last growing season's bountiful harvest, so it seems appropriate that any discussion includes issues related to our food supply. Think climate change affecting crops, groundwater poisoning related to fracking, antibiotics in meat, family farms going bankrupt, etc.
You may want to ask your guests why hunger still exists in a country that routinely enjoys bountiful harvests.