Dris
I would put my glad rags on and go with my head held high. I have been in a situtation (regularly) where a chap with whom there is "previous" invites me to dos. I go, I am polite, charming and conduct myself with dignity. Because of our previous history, his happiness is important to me. But I am prepared to rise above the past and show that I can conduct myself with grace.
Given that it is only a few minutes walk, you can always come home if you feel out of sorts, but you may well feel that you can stay given you have the safety net of living just a hop skip and a jump away.
I am in a similar situation. My friend from college (whom I have not seen for 20 years and whom because of my ex husband I stupidly fell out with) is getting married in December. I suspect as an olive branch she has invited me. I will not know a soul at the wedding apart from the bride and her parents and it is 2 hours drive from here. However, I am planning to put the face on, put the glad rags and go and wish her well. (I will however, arrange to stay with my parents or a friend in case it is terrible).
Go for it lady. You never know, you may even enjoy it!
BMx