[…] As someone who is on the fence between agnostic/atheist, I bow my head when I visit family who are religious. Their table, their rules, and I think it is respectful. OTOH, when my religious family comes to my house, they can pray silently to themselves if they want while I dig in and talk to others, because it's my house now.
For me this pretty much hits it on the head. It’s about circumstance, right?. Family? Friends? Work party? Close family- I know we are all Roman Catholic religious so no problem we all say our particular version of grace. Over thanksgiving I was with my brother’s family, who is Methodist. We kinda traded out who said grace first for which meal, and for the sake of our (very young) kids we then said the other family’s version second. But in years past we’ve all been adults about it and whoever doesn’t say it out loud just takes a few more seconds to themselves before digging in.
If I have some of my non-religious friends over, yah, I expect them to tolerate me saying grace with my family, but I don’t expect them to participate or do anything other than sit/stand quietly for 30 seconds. In return I don’t expect anything over at their places- they just see me go quiet for a few seconds (in your head goes a lot faster than out loud). I mean, spreading the faith is great and all, but you aren't gonna win any converts by forcing people to listen to a 30 second spiel once in a blue moon. What are you really trying to accomplish in that setting? Are you really trying to say thanks, or are you trying to show off how pious you are? Don't let left hand know what your right is doing, and all that.
What if, at a large non-family gathering, someone running the show grabbed the mike to say “Hey food is ready. Feel free to go ahead and start eating- if you want to say grace then bow your heads with me…” Would that be awkward?