I have mixed feelings about this (not that you should care how I feel). On the one hand, that sounds like a lot of fun and if your invited guests and family won't be shocked or offended by it, that's great. Just remember that as a crossdresser, you will probably do too good a job of dressing as a woman and people will know that this isn't the first time you have dressed as a woman.
On the other hand, I may be considered a bit "old school", but it seems like the both of you aren't taking this wedding very seriously. A wedding is traditionally a serious ceremony where there is a lifetime commitment. What will you or your friends and relatives think when you pull out the wedding photos twenty years from now? What will your children think?
Just something to think about.