O.K. Roughly speaking, the Gaidhlig would be 'Fuil na h-Alba, Meadhan Amerighan.' That means pretty much, 'Blood of Scotland, American heart.' (Heart as in your soul or core, not the organ.) There's no real easy way to say 'Scottish blood' in the Gaidhlig that is grammatically correct.

I would say if you get the chance email someone at the SMO to double check because my Gaidhlig is far from perfect.

As far as the tattoo, I echo what these guys have said about thinking about it, but you are obviously pretty sensible of the fact since you are carefully planning it rather than just going out and getting it right away. Good luck getting it done!