By Plurals, Colloquial expressions

Hi, Thanks to those programs, my English is getting better. The narrators speak slowly, clearly, and precisely. My vocabulary chest is filling up gradually. However, I wish I could watch series about relationship and interaction between family members or people in regular daily life....

And, oddly enough, "Who all is coming to dinner" sounds better to me than "who all are coming to dinner", even with the reference to a plural.Thanks Philip. Is "Who all ....." a colloquial expression? How about in writing? If a teacher shows a picture to the students with two boys under the...