Just remember that this is a free country. You don't want anyone to tell you how to raise your kids, so don't tell others what to do either, just because it doesn't fall in line with your values. I am sure there are worse mothers than the ones who breast feed their offspring all the way to kindergarten!
In general the US population is way to uptight on any subject involving nakedness, including breast feeding. This probably goes back to puritan ethics but is deeply rooted. I think it screws up everyone's sexuality, increases STDs, teen pregnancy rates and sales of porn.
G