If you can't carryon your wedding dress, then try using that clear drycleaner plastic thing over it to avoid any "dirty hands" from touching it. Also, try to learn the spanish phrase for "this is my wedding dress, i don't want my husband to see it" or something similar.
MOst of the customs people are actually quite pleasant. I had one in Varadero a few years ago - he was scrutinizing my passport and i was getting very nervous. Then he said "you have been to many many nice places" then he starting asking where the stamps were from and what the places were like. Then he wished me a pleasant holiday and waved goodbye as i exited the little booth.
