Formal:
* E ʻoluʻolu e leʻaleʻa. (Eh oh-loo-oo-eh leh-ah-leh-ah) - This literally translates to "Please enjoy yourself." It's a polite and formal way to say "have a nice time."
Informal:
* E ʻoluʻolu. (Eh oh-loo-oo-eh) - This means "Please" and can be used in place of "Have a nice time" in a casual setting.
* E leʻaleʻa. (Eh leh-ah-leh-ah) - This simply means "Have fun" and is a very common way to say "have a nice time."
* Mahalo nui loa. (Mah-ha-loh noo-ee lo-ah) - This means "Thank you very much," but can also be used to express gratitude for someone's company or to wish them well, similar to "have a nice time."
Bonus:
* If you want to be really specific about the type of fun they should have, you can add a descriptive word after "e leʻaleʻa." For example:
* E leʻaleʻa i ka ʻaukai. (Eh leh-ah-leh-ah ee ka ow-kai) - Have fun swimming.
* E leʻaleʻa i ka ʻai. (Eh leh-ah-leh-ah ee ka eye) - Have fun eating.
Ultimately, the best way to say "have a nice time" in Hawaiian depends on the context and your relationship with the person you are speaking to.