Hi Marek,
If the archers are charging they do not get to shoot.
I am puzzled by your second question. If the cavalry charged the archers, the archers should be contacted and therefore do not move. (If the cavalry couldn't reach the archers, then they could not charge).
The wheel must be at the start of the charge. The maximum move distance is the normal move for a wheel. It is a wheel NOT a turn. A wheel of 90 degrees in Pacto should twice the square root of 2 (Pythagoras) so about 2.83 HBW. So loose cavalry wheeling 90 and then moving should end up moving up to 2.17 HBW after the wheel.
Richard