Regarding the take off performance, there 's no question: Use the head wind.
For landind it's a little bit different, and it's an airline policy, actually you have the choice between flying Vref over threshold and use the head wind correction, or flying Vapp. In that case, overspeed and head wind will counteract so you can't recalculate your landind distance with headwind, you consider no wind performance. Embraer works like that, in the AFM they write there's no difference between a landing at Vreff without wind, and a landing at Vref+20 with 20 knots of head wind. Of course you can fly your approach at Vref and recalculate your landing perf with 20 knots of head wind, but your margin regarding stall is not comfortable especially without auto-thrust.
rgds