What is 2 demigods kid how Godly would it be?

It would be another demigod because you are half less than your what your parents are. So, your dad would be 50%-25%=25%, then the mum would have the same equation (50%-25%=25%), the last equation is 25%+25%=50%, and since a demigod is half god (a mortal parent and the other a God)then it would not be a demigod -aka half-blood- then it would not be a demigod -aka half-blood- logically it would be a quarter-blood (not a demigod).