As for your wife, let her know that your respect her point of view. If she feels confident that you do respect her side, then you can open up a nice dialogue and share your views with her. I am so tired, but I don't want to end this before it is the right time for her. First, I want to commend you for nursing your child as long as you have. The World Health Organization now recommends that women breastfeed their babies for two years.
Children receive a lot of immunities and are generally healthier if they are breastfed.
However, children not breastfed can be very healthy, too. I nursed my first child until he was about 3 years old, and when I did wean him, I felt the same way you did. I weaned him in one day, and he is just fine and has no psychological problems from this whatsoever. I put a bitter tasting herb on myself, and when he went to nurse, he didn't want to anymore. I then told him that because he was a big boy now, I have no more milk.