Do you have blue eyes? apparently us blue eyed people are more susceptible to crying from onions LOL.

Agree - first option would be to get DH to do it!!

I've tried the fridge... hasn't worked for me.. the theory with that I think is that there is less vapour from the onion if it's cold.

For that many onions I would get out my v-slicer thing. Or if you have a chopper blade thingy for a food processor (magic bullet comes to mind! hahahha) then use that. No way would I stand there manually chopping 5kg of onions. ugh.

Have fun!