Eliminate

Informal formal wedding tomorrow and I have the role of Best Woman or something like that. The majority of the celebrations seem to involve prosecco at The Balmoral which is a rather lovely way to spend a Friday. But what to wear?
Considerations: End of March, weather, windyness ( not mine) hmmm need to be able to walk whilst fuelled with fizzy pop, hat? No hat? Hair up. Hair down posh enough for The Balmoral, not too posh for Princes Street, cute and still cute twelve hours later when the party ends.... Ooooh the pressure of a decision!