No, you can choose to picture super hot girls (or whatever works for you, ain't going to check your bio to find out your gender, that's not the point) in your mind while they pray. How are they going to know?... just don't think out loud

When my younger brother gets his turn he abuses the privilege basically preaching long enough to cool the mashed potatoes. It irritates the snot out of me. Since my parents know not to ask the non-believers among us to pray, he gets the opportunity rather often. Now I'm thinking I might request a turn next year. I'd like to hold hands around the table and request a moment of silent thanks giving.

If it is, it's the weakest attempt anyone has made on me.

I have not experienced this. I never prayed before the meal. Though I was raised Jewish (and in my sect of Judaism we believe God to just be a residual force in all humanity, not some Dumbledore on a cloud in the sky supernaturally controlling everything) I've attended Thanksgiving with my Catholic and Christian family members. They just say a short grace before the meal. We're all respectful of our different opinions and views on the world. We don't think the Thanksgiving table is a place to argue. It's meant to be family time and enjoy each other's company.

Well, in my family, I don't look at it that way. My family are believers but accept that I am not. I respect their rights to believe as they do, and they feel the same toward me. When we sit down around the table and everyone bows their heads, I don't. I just look around at all of them and think about how much I love them all. Sometimes there is no agenda, just family being family.