There shouldn't be a moisture problem with above-grade concrete. Are you sure it is concrete and not soft like a gypsum product? In either case, you don't really want to put fasteners through it.
A floating engineered wooden floor of any size, really doesn't move. I have it in my first floor, and the weight of the stuff is just so much, along with the friction to the underlayment, that it is solid. Like any wooden floor, you do need to leave an expansion joint around the edges. I was really impressed the the stuff from Kahrs - the only thing they make is wooden flooring, and have been doing it since the 1850's. Many of the engineered stuff can be glued down, or floated. Read the specs carefully. Repair or replacement is much easier if it is floated.