Sheesh...

If at all possible, I recommend an instrument mike in addition to your vocal mike for reasons given above... in my case, I sing low baritone-mid bass range, and drive the poor sound man to fits when I suddenly chime in with the whistle.

Barring that, during sound check play with distance from the mic. I find that for me, I usually have to be between 4"-6" away from a mic that will also carry vocals for me. Your mileage may vary.

M