i think a character buffet dinner would be just fine for an intimiate wedding and i think your bridal attire would be no problem as the 2 buffets you're looking at are at wdw resorts.
we had a large family vacation at wdw before where all 25 of us went to 1900 park fare for the character meal, it was a casual dinner but the grand floridian made it very special with its great ambiance & in my opinion 1900 has the best food of the character buffet dinners outside the parks. At dinner time they now have cinderella & friends at the 1900, so great photo op's too. Although chef mickeys is nice & a close runner up. it has a more modern fun wdw atmosphere i'd say. the disney 2005 birnbaums addition says the dinners cost $26/ per adult & $11 per child at both these buffets.
you can also get some fun pictures with the monorail at either resort, i saw anothers bride's picture with the monorail & was suprised how much i loved it & how great it was!
best of luck with all your plans!
twojo21