Im not in favour of a ban - they just make people resentful and we just end up being lumped in with all the not -PC fun police- I agree that awareness is the way forward.
You do need a bit of diplomacy as well, many balloon releases are to support very worthwhile charities , "never mind the terminally ill childrens hospice what about the turtles" isnt always the most helpful message
Letting people you know you support their cause and suggesting equally interesting alternative fundraising actvities works better.