So…there will be many different opinions on this one.
My take on it is: WHY are you doing both? I first thought it was because HI is difficult for people to get to, but you’ve already got close to 200 guests coming to that one and fewer coming to the civil ceremony. Most people do a civil ceremony ahead of the big event for insurance purposes or because someone’s in the military or something.
But then again, it sounds like you’ve already committed to both events, so based on that, my two pieces of advice are:
1. I’m a person who believes that if you already got married, then you are married, and the 2nd event should not masquerade as a wedding. For that reason, I think that the only courteous (and truthful) option to your guests is to make it clear in the invitation that they are going to be attending a celebration of your marriage–NOT a wedding. I also did a civil ceremony and then a larger reception a few months later, and our invite announced when we were married and then people were invited to a “celebratory brunch.” The reason is because a wedding is a special event–the kind of thing that people will request time off work to attend, purchase plane tickets to attend, spend $100 on a blender to attend, buy a special dress to attend and so on and so forth. But not everyone will do all that for a reception without the ceremony–it’s just doesn’t have the same social/cultural significance. It’s irresponsible and misleading to imply to people that they WILL be witnessing a wedding when you, in fact, have already been married. In other words, call the event properly by what it is and allow people to make their own decisions.
The other issue that’s specific to YOUR case as well is that while some people violate the above advice and DO have a private civil ceremony and then a big wedding later, those people are generally people that keep their civil ceremony ultra-secret and private (again, usually for more prosaic reasons, like getting someone on healthcare or doing something with taxes or because of military stuff). You’ve already got 50 attendants at the civil ceremony–word will get out and there’s no way that at least one of the HI isn’t going to hear that they’re attending a 2nd ceremony. Your risk of your guests feeling lied to is that much higher because of the number of people who will know about the first ceremony. And there’s also the unpleasantness of people feeing like they were lied to because they weren’t “good enough” to be included for the first ceremony–you dont’ want people assuming that, so I think it’s much better for YOU in your particular situation to be upfront.
2. Having said that, you CAN do pretty much whatever you want so long as you let guests know that you are technically already married. You can wear your dress, you can repeat your vows, you can cut cake and all that. In fact, it probably WOULD be a nice gesture to stand up ahead of the start of the reception and repeat your vows. I personally think that attendants walking in ahead of you might be a bit too much ceremony, but perhaps your friends can stand with you and do something nice, like give a couple readings or something like that. In other words, just because it won’t be an official wedding doesn’t mean that you can’t do things to give it a sense of occasion.