Happy Children's Day. Edit: "Ia manuia le aso fanau" translates literally to "Have a blessed/happy birthday". Manuia - blessed; fiafia - happy.
Manuia le uikegi = Have a good weekend or Manuia lou uikegi = You have a good weekend
Manuia le asofanau, ma ia maua se aso maoa'e.
"Ia manuia le aso" (Have a blessed/safe/lovely day). "Ia maua se aso manaia" (May you have a nice (manaia) day).
Ia manuia le aso
Happy Mothers Day - Ia manuia le aso sa a Tina.
Ia maua sou Aso Lulu lelei ma le manuia.
shehoneeun- [seehoneen]thats how you say it.
Happy Valentines Day = Ia manuia le aso Valentine.
Have a good day
Va'ai fa'alelei
"Happy Anniversary" - "Manuia le Fa'amanatuga". To be specific, you would need to say what the Anniversary is. Example - Happy 50th Wedding Anniversary" - "Manuia le fa'amanatuina o le 50 tausaga o la oulua fa'aipoipoga" or "Manuia le fa'amanatuina o le 50 tausaga o la oulua fa'atasiga". "Fa'aipoipoga" is "wedding"; "fa'atasiga" is "togetherness" or "being together".
Goodnight - "Manuia le po", "Po manuia" or "Po lelei".