As long as the take-off's been calculated to account for the increased drag from leaving the gear down longer
No need to change the take-off figures. The whole thing is based on an engine failing at V1, if that engine is still runnning past V1 you will meet the required climb gradients and clearances easily even with the gear down, if a engine fails whilst the gear is down you would select it up anyway. There are however big penalties for departing with the gear locked down which is a different situation.