Here's -- Plurality Question
Solution 1:
Lots of idiomatic usages are "grammatically incorrect". You can analyse this particular one to find supposed justifications for it being in some way "grammatical", but the fact of the matter is even educated speakers commonly say things like Here's John and Mary, and Where's the scissors?
Part of what's involved here is proximity agreement (aka the proximity principle) which causes us to inflect the verb according to the first subject, even if there are others following.
I believe it's also relevant that we tend to do this more often when the subjects ("subject", with something like scissors which are grammatically plural but semantically singular) are perceived as a single thing. Thus, "the news" is effectively one thing containing some good and some bad parts. And John and Mary are being spoken of as one couple arriving, rather than two separate people.
Solution 2:
I perceive it as "Here's the good news and [here is] the bad news."
Solution 3:
It rather looks as if here's, like there's, is becoming an invariable expression, used to introduce either one or several things, events or ideas. So we might say 'Here's a few ideas to throw around', just as we might say 'There's a pub, a railway station and a shop in my village'.
Solution 4:
The people who say 'It's 100% wrong' or the equivalent are self-appointed arbiters. Here is a less arrogant stance given as long ago as 2005 on EnglishForums [tidied]:
"There/Here is" with plural subject: [is this] allowed?
Please help [me] to decide. Is it just a common mistake, that even native English speakers make, or is it actually correct English? And if so, when is it appropriate to use this form?
Thanks in advance
Ralf 2nd January 2005
REPLY Mister Micawber: Hi Ralf,
[It is] still considered ungrammatical by many, and you would be wise to avoid [it] in careful writing. But the fact remains that the use of 'here/there is' (usually as 'here's/there's') with plural nouns is extremely common-- and acceptable-- informally. I use them myself frequently when I speak.
One might ask the prescriptivists whether they allow 'It's me' or 'It's us', as probably 99+% of natural speakers use them.