Children always appreciate small gifts of money. Mum or dad, of course, provide a regular supply of pocket money, but uncles and aunts are always a source of extra income.
This is a sentence from "New Concept English", which is the most popular English textbook in China. But I have two questions about the grammar.
Shouldn't we use "provides" instead of "provide"? (Because "dad" is a singular noun.)
Shouldn't we use "are always sources of" instead of "are always a source of"? (Because "uncles and aunts" are two sources, and there is an "are".)