RF from wireless networking gear *cannot* under any circumstances harm you.
Q. How can a young child or baby tell you if they have a headache when near wi-fi or a mobile mast?
A. They can't, they just live with the constant pain and become moody or quiet.
Uhm, no. they don't get a headache from being near wifi. The reason they're probably moody or quiet is because they've got gas from the mungbean and soy juice drink you've given them in place of milk.
If you shine a fairly bright torch at your hand, more electromagnetic energy is hitting you than from a wireless network card. Do you get headaches from having a torch shone at you?
Anyone who says that wifi equipment or mobile phone masts make them ill is insane. Actually properly delusional insane requiring prompt psychiatric intervention kind of insane.