Hmmm....
Stressful situation.
The first thing I would do, is talk with your fiance about it. Ask how he feels. Also, how are the ground rules with the two of YOU regarding your families? How is the stress between the two of you, and its bearing on your relationship, when arguments and things happen?
If the two of you fight about them, then that would be something that needs to be worked through before marriage.
Also, here is some advice.

This is one of the best bits of marital advice that I have EVER received, and I believe in it 100%:
When you and your husband have fights or arguments, don't call family to discuss it with them/vent. EVER. This is honestly one of the biggest things that causes in-laws to dislike each other. Seriously. A girl gets into a fight with her boyfriend, goes and cries to her mom and sister about it, then makes up with boyfriend. She forgives him, the mom and sis do not-because they are looking out for their sister/daughter. The same goes with the boyfriend if he spouts off about his girlfriend to family/friends. The more family that is in your business, the worse it is.
So, if you ever want your families to get along, that is the best advice I can give-unless it is a matter of cheating (where you plan on splitting up for GOOD), domestic abuse, or that sort of thing, etc. then keep it to yourself. Don't tell family about all of the little tiffs.

You forgive and forget, they never do.
As far as the wedding...have whatever kind of wedding you want to have, but make your requests upfront. They behave, or someone will escort them out. (Get big burly friends as your ushers for the wedding/bouncers for the reception.

)
Seriously. Let them know that this day is about the two of you, and not about everyone else's grievances...and you kindly ask that they keep it that way, or not to come.