Your sentence is the question form of
"There is music, dancing and margaritas."
This is an inverted sentence, where the subject comes AFTER the verb; AND the verb agrees with the first noun of the subject. Here, it is the singular "music", so we need the singular verb 'is'.
We do not have a context, but it sounds odd, written in the Present Tense. Are you sure you don't mean:
"Will there be music, dancing…?"