Will Campy Mirage 9 speed crankset work OK with 10 speed..
 

I know it is not ideal but will a Campy Mirage Triple 9 speed crankset work ok with Campy 10 speed group..

I already have the triple specific FD and Medium Cage RD, so all I need is a triple crankset a friend has a mirage crankset that is a few years old..

"work ok" is strictly subjective. What works okay for you might be heinous for someone else. All you can do is try it and see.

It will most likely work just fine, try it and see.

Yea, pretty sure your chainrings could care less how many gears are in the back. You can experiment and so single speed with that "9 speed crankset".