We hope the sickness will pass soon and that you are back up to snuff! They say the mother is the first sense what the sex of the baby is, I did both times. Can't wait!!
Take a deep breath, it appears that you all prep you are ready to go!!! Think about the reason for all the hard work and focus on you and your FI. Have fun and enjoy the time together! Everything will work outand fall into place when the day comes!!!
I concur with the previous responses - if you communicate your plans to your guests ahead of time, so that they can make plans to attend, then you can go ahead and send out the invitations without having to send out the std's. Happy planning!