Interesting idea! A few thoughts to share: I would love to see a few "pre-built" themes/templates to choose and draw inspirations from. I once saw a youtube clip of a Star Wars-themed wedding and thought "hey that is not a bad idea for my future wedding", so I think it may be interesting for your site to curate those information first and build different themes.

The benefits are twofold: customers can get a flavour of what your platform can offer (say, for my case, I would think "oh hey that Star Wars wedding theme is listed here! My idea of such a wedding wasn't so crazy after all); vendors that specialise in certain niche themes can have a chance to be featured in your platform, which hopefully leads to more sales.

Well, best of luck to you! It's unusual to see couples building tech companies together :)