As a family of practicing atheists, we often face this situation in family gatherings. As a solution in our home, before every meal whther we have guests or only immediate family, we say “Thank you for this lovely meal.” That covers pretty much everything. You choose whether you are thanking the farmers who grew the food, whoever bought or prepared it, the animals or plants who gave their lives, this marvy existence that inclues things like tasty tidbits, any fictional beings you wish, or anyone/thing else. It felt awkward for us to say, “We don’t say grace, but I know some of want to, so go ahead if you wish.” Faced the situation often because both my family and my spouse’s profess to be Christian (whether they exhibit “Christian” values is another discussion). And a good share of family gatherings happen on what are their high holy days. They just don’t seem to want to accept Samhein!
I feel our “thanks” beats the heartfelt blessings I grew up with in a strongly RC household. How did it go? As I recall, we said in one breath and as quickly as possible: “Blessesegiftswe’rebouddareceivefrommabodynblooddaChrisamen.”
(Along the same lines, I always wondered how vaguely you could wave your hand in front of you and have it still count as an official sign of the cross.)
In someone else’s house I just remain silent. You picks your battles.
Peace be with you all.