"Every man and his dog" feminine equivalent
Solution 1:
Some online dictionaries, like Wiktionary, suggest everyone and their dog or everybody and their dog as non-gender versions of every man and his dog. These have been in use for a while. For instance, here is an excerpt from "Reminisces" in The Railway Agent and Station Agent magazine from February 1894:
Everybody and their dog in that town had the 'fever and ague,' and they walked about like ghosts.
One can also make this idiom feminine in one of two ways: switching every man or everyone to every woman (or girl, lady); switching their dog for their mother or another female figure. Some of these are constructions used to specify women instead of men, e.g.:
Her scathing observation was that 'it must be obvious to every woman and her dog that this is a male document about a male future where Nation-Family-Father-Son are united in their diverse control, and where the situation of women, far less a feminist alternative, barely rates a whisper' (Martin 1984:57). (Google Books)
Others specify groups irrespective of gender, particularly if everyone or everybody leads the phrase:
Everybody and their mother was on there. (Google Books)
'Everyone and their brother has a gun.' 'You mean everyone and their mother.' 'What?' Everyone has a mother, not a brother. That's the saying. "Everyone and their mother." ' (Google Books)
Solution 2:
Google shows some hits for "every person and their dog", e.g. Central Western Daily (Australia), Newcastle Herald (Australia), Barnet Council (UK), even someone on Stack Overflow. "Every woman and her dog" is sometimes seen but appears to have less currency outside very casual writing (social media posts, etc).
Perhaps a better alternative is "all and sundry", which Collins defines as "all the various people, individually and collectively"; it carries a similar, slightly dismissive (or condescending) connotation to "every man and his dog".
"Old Uncle Tom Cobley and all" is another (slightly humorous and probably British) expression meaning everyone, from the folk song Widecombe Fair.
If you're wanting to avoid the slightly negative connotation, you could say something like "The whole world was at the amusement park", a classic example of hyperbole (Reader's Digest.