If you're keeping your eyes open, I recommend the following sort of placement:
The eyelids can rest half-open, or however resting them while open happens for you. At this point you're set to jump into anapanasati, and eventually the eyes can get lumped together with the rest of the body as a unit which helps to facilitate calming involvement with any of it, eyes and everything else, for the duration of the sit. As a result of these efforts, blinking can then become automatic and not something you fuss over, the same goal as for the breath itself.
Eyes flitting about, etc, can sometimes trigger mindfulness, moreso with practice.
Just don't sit through knee pain.