The same exact thing happend to me. My nikkah took place at themasjid and after my dad arranged a dawat-like for the family in a small community hall, and i had it all worked out but right after nikkah at the masjid it was decided that we weren’t going to have anything done. instead my in-laws gave an iftar(it was ramadhan) at the masjid in the evening. I couldn’t wear my outside that I had originally chose to wear because it wasn’t there but I ended up wearing a legnga anyways! so just wear it even if it’s fancy