Sister-in-law's birthday (about 367), can I use the word "happiness"? What kind of greeting should I use?

How to send greetings to each other should match each other's living conditions and age. Your sister-in-law is young, so it is a little inappropriate to use the word "happy", but it is not absolutely impossible to use it. If you are 50 or 60 years old and your brother and sister-in-law are very harmonious, you can use this word completely.