I swap 1/2 cup of flour in that recipe for 1/2 cup cocoa. Mmm. A few people asked me for the recipe yesterday (I needed a snack for a mom's group), so they taste better than "not that bad". They're delicious.
Personally, I eat the cookies. I always eat the cookies. I think they can help, but they're not going to give you an oversupply unless you start overpumping.
If your supply isn't good, baby's weight gain will be poor, there will be not enough diapers, and it will show up in the zillion doctors appointments a baby has.