>>There is still a lot of resent because I said I'd get a V after the third kid because a buddy of mine did.<<

Hill this seems to be where your problem lies. You said you would get a vestectomy and now you are not. Some people would see this as a crediblity issue.
I am not arguing the merits of a v I have never thought of getting one myself, but you are stuck with having said you would get one. Where is the follow through?

I can see your wife over the next few months working up and getting her tubes tied. Your sex life will probably improve some what but what you will be left with is, when it comes to the big test, your wife will have followed through and you have not.
I would chop an arm off before I ever let that happen.
How will you mitigate this?