Is it appropriate to say Grace over a meal when there are non-Christians present at the table?
I’m not entirely sure. If you don’t want to make them feel uncomfortable, you could just silently pray by yourself without them knowing.
You should always say grace – i.e., thank God for your food, regardless of who is present. If others who may be present are uncomfortable, too bad. Maybe it will make them think.
When it’s just us, we say grace normally. “Bless us O Lord, and these thy gifts, which we are about to receive, from thy bounty, through Christ our Lord, Amen.”
When we have non-Catholic Christian friends over, grace usually stays the same.
Sometimes, when we have Jewish friends over, we say a blessing that’s less specifically Christian.
Growing up, we used to include the Morning Offering or the Angelus with grace at breakfast or lunch, respectively. When we had company, we tended to exclude those additional prayers from our routine and merely said them privately to ourselves later.