I am sending positive thoughts your way. I agree with all the other ladies on trying to communicate with your folks, but let me also say that in the end, you and your honey will be married. You are celebrating your love for one another. Please don't let others actions dampen your celebration of love. It will mean as much and be just as special whether they choose to be there or not. It is their choice and you cannot make it for them as much as you would like to. They also have to be the ones to live with whatever flows from their choice.
Lots of happy thoughts from me and love to you and your FI. Your day will be wonderful and special no matter what!