宁愿你快乐，亲爱的。

I'd rather you are happy,dear 这种说法一般是遇到了什么困难 你要牺牲一些

I prefer you are happy,darling这种说法是纯生活的~~~表示自己的希望

my dear,I wish you were happy

Dear,Wish you to be happy或者Dear,I hope that you can be happy.

dear ,I'd rather you are happy.
dear, I hope you can be happy.
dear, I wish you are happy.
dear, I prefer you are happy.

i hope you will be happy forever, my sweet!

I prefer you are happy,darling.