I haven't seen these pins on sale in shops myself, but my usual experience of various charity pins sold in shops is that they are in a box clearly marked with the named charity for which they are raising money/raising awareness - so it is unlikely that people buying them would be confused as to where their money is going.
I wear a forget-me-not pin, one that I obtained through the Alzheimer's Society. Until now I had never heard of any link the flower has with freemasons and nobody has ever mistaken my wearing it as anything other than in support of dementia awareness.