'It's my cup of tea' is a British saying that means 'It's something I really like and am comfortable with'. The opposite is also used 'It's not my cup of tea.' During work hours we can refer to the short break we take for a drink, even if we might drink coffee, as a 'tea break. 'A storm in a tea cup' means a there's a big fuss about something trivial.

'The cream of something' means the very best examples of it, so yes, it is like saying the elite. A fete is an outdoor event like a garden party. Fate (pronounced the same way) means destiny - what will happen to us. I think this is the meaning you need. 'When we reach adulthood, fate will take us in different directions' or you could say 'When we become adults, we'll follow different paths through life.'