It's useless to use floats, from my 2D in 3D discoveries, as the alignments is still as precise in ints as it is in floats. PLus, you might save some CPU.
On the contrary, it's useless to use anything =other= than floats with delta time. What's the point of a delta multiplier if you're only able to judge it to the nearest integer? It's like measuring an atom with a yardstick. Even if you're not drawing at sub-pixel coordinates, you should still be calcuating at sub-pixel coordinates. And if you can notice the time difference between a handful integer multiplications and a handgful of floating point multiplications, there's something seriously wrong with your code.