YOU SAID:
I want to wish them a grand birthday
INTO JAPANESE
彼らに盛大な誕生日を祝いたいです
BACK INTO ENGLISH
I wish them a happy birthday
INTO JAPANESE
彼らのお誕生日おめでとうございます
BACK INTO ENGLISH
happy birthday to them
INTO JAPANESE
彼らにお誕生日おめでとう
BACK INTO ENGLISH
happy birthday to them
Yes! You've got it man! You've got it