Cleaning wedding dress

We are having our minimony on our original date, this Saturday, May 30th, and I will be wearing my wedding dress. We are planning a full wedding and reception for next year, and I plan to wear the same dress for both events. Our minimony and sequel wedding are both happening at our venue, a farm with all dirt/gravel parking areas and pathways and a grassy hillside ceremony site. The forecast calls for rain all morning on Saturday, tapering off just an hour or two before our ceremony.

My dress is lace with a long train and it is super important to me that the first time my FH sees me in it that my dress is displayed in it's full glory, train splayed out and all, and I don't want to have to do my vows with the train bustled. We are planning to do vows, a first dance, champagne toast, and cake cutting. I'm a bit worried my dress will get trashed because everything will be wet. Our local dry cleaners is open (thank goodness) but super limited hours, so if my dress gets muddy or grass stains, I won't be able to bring it in for cleaning for at least a couple of days following our ceremony.

Does anyone have any recommendations for what to do with my dress right away if it does get dirty? Should I try to rinse out the dirt with water or would that make it worse or possibly damage the dress? Should I let the fabric dry with mud or grass on it? I want to remove any dirt and limit the possibility of stains or damage to the material. Any suggestions at all are helpful!