Have fun!

Nanny: have fun!
how do you say 'have fun!' in chinese?
Min: I don't think we have special words for it.
Nanny: ok, depends on what one is going to do?
Min: 玩得好
玩得高兴
Nanny: thank you
Min: yes, it depends on what one is going to do and now I can't think of anything similar for have fun.

玩得高兴
wan2 de gao1 xing4