My niece gave me her wedding dress that was in her closet, for 30 years, she didn't do anything to the dress before she put it away just rolled it in a ball & put it in a bag. It was a mess, but she wanted a christening dress made from it. It was a satin dress, I didn't want to pay for cleaning ,so I washed it by hand in woollit & it came out pretty clean.
This is what I ended up making from it.
So go for it, I know it is scary to start cutting it up, but what else will they do with it. So I say try...Good Luck