Formal attire is required. How dressy is too dressy, etc?
It's a bit like a weekend of pampering, being looked after & it's sort of meant to be a surprise so we don't know what to expect and that's all the details we were given. So knowing as little as I know, what would you turn up in or expect that people would be wearing? It's not a business function but there will be well known business people there.