My parents run a wedding venue in the USA. Usually wedding vendors (FOOD, VENUE, DJ, photography, etc.) have local conventions. I would find the local wedding venues and talk to one of them, find out where and how they advertise and do the same. Go to the stupid conventions or events.
Assuming the wedding business in France is similar, doing this should get you most of the information you need.
Idea sounds neat, but in my opinion the less people have your information the better. Seems like just another opportunity for a company to get hacked and loose all your information.
Yep good luck