I envy you all for being able to play with your seating charts like that. My parents are both divorced and I have decent size families on both sides, so I have to make sure to seat them on either side of the dance floor. They get along civilly, but anything to make the day easier. Then my dad re-married and then got divorced again. My step-mom will be there and I just found out she has had a boyfriend for the last year and a half... Then there is my FI's families, not only are his parents divorced, but he was raised by his grandma and she doesn't know that he talks to his dad. His dad will not only be at the wedding, but is helping us pay for it. Sorry for the venting... It has been one of the more stressful points of the planning.
theDame~ I say go for it and have fun! I don't think it is mean, it is a great way for your friends and family to get to know each other. After all, they are all there to celebrate you and your FI. To make it more interesting, maybe make up "20 questions" to ask each other to help break the ice.