What to wear this Saturday tea party

I am so happy got the invitation to go high tea party at five stars hotel. The theme is casual so I am thinking what and which clothes to wear. I have make up my mind for tonight event, I and my friend will go together she coming to get me from Damansara. The event at the hotel so I need wear formal. I found two blue dresses, I am choosing one of it and match with cardigan. I try snap pics later, not sure if I am going to wear make up I just worry it melt in this hot weather.