Well, consider it's gonna be quite cold. Jan and Feb are the coldest months here.
We put on 5mm (and more) wetsuit, hood and boots.
'bout the wind you should keep under control Windfinder then book your flight.
Sardinia quite often provides "surprises" and the Island is just great. I love it.
Also Sicily is quite nice and warmer than the northern part.
By the way we had 40 kts winds blowing 'till 2 days ago...
I suggest you take contact with some "local club" before planning the trip. Just look for their kite club in google. ( i.e. kitesurfing sardinia ...)