If they do not know just how much you have, make a show of getting rid of some items. Using them up during camping trips, giving to food banks (foods that need rotating), send them to a disaster area, buy a few cheap things and have a yard sale to get rid of 'all' your preps, complain loudly and widely about your worthless distant relative you have had to send your preps to so they could live on them.
Just a few ideas off the top of my head.