翻译成“善意的谎言”可能比较好

you know that a lie is a lie. To tell someone a lie just so they will not feel the pain or to hide something (like a surprise birthday party) is usually accepted as a "little White Lie" and I think your "delightfully small rumor" is a cute way of expressing it. When I refer to it in my speech, I usually say : "It is an honest to good true fairy tale". so I am telling the person that what I am saying is in fact NOT TRUE but most people do not hear the message and believe what I said as the truth. THEN I DID NOT LIE. Of course I use a combination of words that the brain misinterprets. Therein lies the fun in a "little white lie" or a "true fairy tale". YES?

花言巧語

i do not think there is a literally matched saying for sweet little lies in chinese. and 悦耳的小谎言 is not a common collocation in chinese, to me, it sounds a little strange. but i can give you a few example sentences, for your reference. 有的时候，伊丽莎白也会撒一些无伤大雅的小谎。wu/ shang- da\ ya\/ is kind of no big deal, nothing serious. “我不想再听你这些动听的话（谎言）了！”伊丽莎白对男友生气地说。 一般来说(generally speaking)，人们都喜欢听悦耳的话，伊丽莎白也不例外(can not be an exception)。but in most of cases, people use 悦耳 to say a sound, a voice, or a tone sounds pleasant. 甜蜜的谎言 is usually used to say a man lies to a woman in order to get her love(of course you can use it in cases a woman lies to a man...). ex. 她再也不相信他那甜蜜的谎言了。and there is an idiom means the same as 甜蜜的谎言, it's 甜言蜜语. as for 善意的谎言, i think you understand it.

The translation can not be directly tranlated, 悦耳的小谎言is much better than 善意的谎言. 悦耳的小谎言means sweet little lies ( It is plesant, people love to hear) 善意的谎言 means good little lies ( the lies may be good or bad, it is not necessary to be good.) Most people in China want to hear only the good news, even though it is a lie. That's what we called superstition. 善意的谎言also means that the lie is benefit to the listener(s). How about it isn't ? then you are a liar.