From Longman Dictionary of Contemporary Englishbe all sweetness and lightbe all sweetness and lighta) to behave in a way that is very pleasant and friendly, especially when you do not normally behave like this She’s all sweetness and light when Paul’s around. b) to be enjoyable and without problems Life is not all sweetness and light. → sweetness
Examples from the Corpus
be all sweetness and light• The negotiations were not all sweetness and light. 