I kite with contacts and don’t have many dramas, but do lose a lens once in a while. The wind tends to dry the eyes out (which is bad for contacts), and wearing sunnies seems to help keep the wind off the eyeballs. You may also want to keep some saline solution nearby in case your eyes get dry.
Important tip to maintain a long lasting relationship with your contacts: Close eyes prior to face impacting the water.

(Sounds obvious, but it aint always that easy!) I had a nice face-plant not so long ago, where I lost one of the lenses from my sunnies, as well as the contact lens in the same eye. Talk about ‘dazed and confused’!