If it were me, I would put it on a Facebook page and call it a day. Providing content to and among a loose network of individuals is when Facebook excels. The 'among' aspect is particularly important because letting people vote and comment and post messages is engaging and building all that in and moderating it on a custom built website is 'non-trivial'. Odds are that Facebook will provide better archiving over the years than with a bespoke website simply due to costs and technical knowledge and an interest in maintenance.

To a first approximation, the wedding is going to wind up on Facebook anyway.

Good luck.