I haven't seen the Broadway show, but I have seen the movie. And I liked it very much. But the real Mary Poppins was a much saltier character than the endlessly cheerful version on the screen.
That was the Mary Poppins who, when one of her charges tried to hug her, said, “Kindly do not crush me, Michael! I am not a Sardine in a Tin!”; the Mary Poppins who often had a look of “fury,” who “snaps,” and “sniffs” and “retorts.” That Mary Poppins “never wasted time being nice.”
ADDED: I remember my father taking my sister and me to see Mary Poppins when I was a kid. My sister kept running down the aisle because she wanted to kiss Mary Poppins. But the audience at a matinee showing of a kid's movie is pretty forgiving of this sort of thing, which reminds me of taking my own kid to the movies when he was little.
He adored everything he saw at the movies without reservation. And we saw a lot of crap--I remember The Land Before Time as being particularly obnoxious--but should you encounter Ben on his return from the show he'd tell you he loved whatever he saw. I knew he was growing up when we saw something, I don't remember what, and Ben said he thought that it was kind of hokey.