just keep putting the caches in whatever container you want. If someone is afraid it's a bomb, they'll call the bomb-aquad, who will try to detonate something that won't, because it's not a bomb, and the caller will look stupid. OF course you'll lose your cache...but if it's hidden well, and no one would be able to find it unless they had the coordinates I don't think you'd have to worry about being suspected of planting a bomb.
I just figure its a hazard of the hobby, and if someone does something stupid either by planting illegal substances or bombs in a cache it's a risk we take, just like anything else in life. There were people planting pipe-bombs at K-marts in my area, no one banned shopping.