I have a sort of a complicated situation, so I will do my best to explain it. My parents divorced about 10 years ago, and it was bitter. For a while, my dad's side of the family alienated me and my sister from family events. Over the years, my sister and I have started to fix things and are once again considered part of the family. I'm planning my wedding for September 10, 2011, and I'm in the process of trying to find a reception space. The venue I like can only fit 80 people, max. My FI and I worked on our guest list, and came up with 65 people that we knew would attend. I didn't list any of my cousins due to lack of space and I figured the ones on my dad's side probably wouldn't make effort to come anyway (I come from a good French Catholic Family). Come to find out, several of my cousins on both my mom's side AND my dad's side would like to come to my wedding, and I don't want to turn them away, especially the ones on my dad's side, out of concern of reversing 10 years of fixing things.
So here is my question. Would it be considered rude for me to ask my aunts and uncles if their adult children would be interested in coming to my wedding? For purposes of making sure that I have a venue big enough? My concern is I don't want to find a new reception site and plan a reception for 150 if only 70 are going to show up. I have 10-11 cousins on each side, most of which have significant others and several of them have children too.
Sorry for the long post, any input would be greatly appreciated.

The truth behind a well laced dress