u may hv to re-sync the wiimote to the console. refer to Wii manual, or simply, open the front door of console, check the red button (A) inside; open the wiimote battery compartment, check the red button (B) ?
with batteries installed, press A then press B within 2 seconds, allow the two toys to sync and u're done.
when u change new batteries, the wiimote LEDs flashes. that means it's healthy. don't blame ur son !