You might want to remove the DAT files on the drone......if you can, although, if the buyer knows of them, their abscence might make the buyer wonder why you removed them.
I suspect the DAT file naming scheme is "continuous", if that is correct then removing (if possible) the old DAT files will not reset the counter so if for example the last DAT file was DAT157 the first DAT file the new owner would create is DAT158.
I have a couple of second hand drones and both had the DAT files on them, though none started at DAT001, this causes me to suspect the Drone itself removes or overwrites the oldest DAT files so that there is space in its memory. I have NOT attempted to remove DAT files myself.
If you are going to include an SD card (in the camera) I'd suggest formatting it and then running something like H2testw on the card to overwrite the card in its entirety, then, once H2testw has finished, format the card again.
Reason.....when I get a card I normally run Zar X on it, Zar X is free photo etc. recovery software but during its scan it also creates a 'map' of the card which includes any bad sectors in the card (I want the map, not the recovered images) but you'd be surprised how many images it recovers from apparently empty second hand cards. I believe H2testw writes to all the space that is considered empty and thus over writes these invisible images/movies/data and it appears to put them beyond simple means of recovery such as Zar X
