The vectors $\langle 2, 0,0\rangle$ and $\langle 2,1,0 \rangle$ form a triangle with the area $\dfrac{base \times height}{2}$. However normal vectors are supposed to tell what the area is too, but the normal vector that I just found through wolframalpha is $\langle 0,0,2\rangle$.
$\dfrac{base \times height}{2}$ equals $\dfrac{2 \times 1}{2} = 1$.
What step am I doing wrong here!?
The magnitude of the cross product is the area of the parallelogram with the vectors for sides.
You should multiply by $\frac12$ to get the area of the triangle.