SOS: Cleaning Vintage Linen

HELP ME! I'm trying to get a baptismal gown prepped for Bear's baptism in a few weeks. Thing is, the gown is four generations old. It's delicate and made of very soft linen and lots of lace.

How in heaven's name do I clean this thing?

Somebody please help me...I'll be in big trouble with the in-law's if I bolox the cleaning of this family heirloom!