Hi Martin,
The DMN6068SE N FET that you proposed can handle current up to 5.6A max. The TPS40210 is a high input/output Boost device that has a max current of 6A. Considering the current derate factor for your FET selection, the DMN6068SE N FET may not tolerate the 6A operation.
Please let me know if you have any question or comment on this.
--Hadi