Divorced Parents?

I'm so sorry you are going through this, like planning a wedding isn't hard enough without family drama.
My suggestion, if you are having a large wedding is to put the divorced spouses on opposite sides of the hall so they don't have  to be close to each other ....thats really all i can think of good luck :)

Do a sweetheart table (you and your honey) and then have a bridal party table for just BM and GM

I totally understand. Both my fiance and I have divorced parents that are married... so we have 4 sets of parents between us (8 total parents). It's so hard because there is so much more to consider than if your parents were still together like father-daughter dances, dad walking bride down aisle, unity candle issues, etc.... I have had several fights with my mom because of issues with having divorced parents.... My mom wants to make sure that she is getting more of the spotlight than my stepmom, and of course that is intruding on the wedding! So jeff and I just made the parents have a little of a role as possible in the actual ceremony, that way no one's feelings are hurt and I don't have to deal with upset parents. My dad is still walking me down the aisle though :)
I thought most head tables are just the bride and groom and wedding party. If so, then I would do it that way. We were going to do a seating chart to keep the parents away from each other, but it would be too much work and since they don't like each other anyways, we figured they would stay away from each other.
Also, it's your wedding too, so if you want to invite your mom, you should even if others might not agree. You wouldn't want to exclude her from your happy moment even if it causes some tension. Sorry for such the long comment, but it's nice to know I'm not alone in this situation! It's crazy!

Well I would say that if your dad is paying for the wedding then i would discuss inviting your mom to the wedding. Unless she is any help to you with the wedding she  should not be there. If you and your fiancee are paying for the wedding,.. than you should invite who you both want to. Once again maybe talking to your dad will be all that it will take.