I think this is the most difficult part in the whole tasks in our household...
The kids will soon learn to leave the dirty laundry somewhere else, so the baskets are empty and there are internet (tryk avler modtryk).
I somehow think old-fashioned dog/punishment training are working - what will happen if the don't get their clothes laundered and it's left dirty?!?
Now being serious, can you do something with a strain-gauge, so you can measure the weight of the basket, if it's placed inside the cabinet on a shelf? then you can to improve WAF add a "false" shelf, that the loadcell/ strain-gauge is lying below, so that it actually are hidden
Help to understand strain gauge and load cells: