This isn't an intro to queer concepts/identities broadly, but specifically an intro to Pride -- the parade, etc.
Below is a lightly edited version of the rec list I sent.
Pride Colors (2019) by Robin Stevenson -- board book
I don't think this does as good a job explaining the colors of the pride flag as the Our Rainbow board book (which also includes "Black and Brown for Diversity and Inclusivity"), but it more explicitly conveys the vibes of LGBTQ+ acceptance -- with lines like "Be yourself. Love who you choose." and "I'll love the person you grow to be." as well as images of what appear to be 2 moms and 2 dads holding a kid and lots of rainbows. It also has photographs of litle kids -- which babies love.
It's Pride, Baby! (2024) written by Allen R. Wells (he/him) & illustrated by Dia Valle [last name pronounced "Vah-yay"] (he/they) -- both are Black and from the U.S. South
This is about DC Black [Gay] Pride. Protagonist appears to be a Black daughter of 2 Black dads (one of whom is maybe trans?).I'm kinda meh on the text, but I like that it exists as a book with an entirely Black family (most of the Pride books I've seen are intentionally interracial -- with a Black/brown parent and a white parent; sadly there's very little AAPI rep in queer picturebooks -- but often have a white or light-skinned protagonist kid), and I learned about D.C. Black Pride, which was new to me.
The book is addressed to a child, and one line is, "I am happy with you / And whomever you choose. / Whether it's him / Or her / Or them-- / You Love." Good job normalizing singular they AND polyamory :) (Though the latter is maybe unintentional, since no polyam flags appear in the book.)
There's a couple pages of backmatter that briefly overview DC Black Pride, followed by a page of Pride flags (with identifiers) and some brief tips on "How to support a child who's coming out as LGBTQIA+".
Pride: The Story of Harvey Milk and the Rainbow Flag (2018) written by Rob Sanders & illustrated by Steven Salerno -- bios indicate each uses "he" pronouns
Per the title, this book focuses on Harvey Milk and the creation of the rainbow flag as a Gay Pride symbol (at the time, the pink triangle was the primary symbol used by the community -- which was an act of reclamation, but still, many people understandably wanted something with more positive associations; this is alluded to in the text, but it's only in the backmatter that you learn what the symbol at the time actually was).There's a 2-page spread of lots of people holding rainbow flags, including a cop, which I don't love, but that's the only real pro-cop moment in the book.
I don't know how your kids are about death, but there is a brief mention of the assassination of Harvey Milk and George Moscone.
A little bit more text-heavy than the other books listed here, but not too much so (though obviously I don't know your kids' reading attention span).
There are a few pages of backmatter, including a Harvey Milk timeline and a Rainbow Flag timeline.
'Twas the Night Before Pride (2022) writtten by Joanna McClintick & illustrated by Juana Medina -- bios indicate each uses "she" pronouns and has a wife; Medina is from Colombia
As the title suggests, the structure of this riffs on the poem that starts "'Twas the night before Christmas" (but is actually officially titled "A Visit from St. Nicholas"). The rhythm mostly works and there are only a couple odd rhyme choices.The family is getting ready for Pride the next day, and one of the kids asks the moms to tell the story of the history of Pride.
I really appreciate how much this book makes it clear that the police were the bad guys at Stonewall. (The book also says "queer" in the text, which feels unusual to me for picturebooks.)
Protagonist family is a Black mom and a white mom with Black/brown kids (one walking, one baby).
Granddad's Pride (2023) written and illustrated by Harry Woodgate (they/them)
This is a sweet story about a kid visiting their (gay) grandfather and learning some about Pride and starting a Pride celebration in the grandfather's small coastal town.(Kid is brown, grandfather is white, couples are interracial.)
Pride Puppy! (2021 hardcover, 2024 board book) written by Robin Stevenson & illustrated by Julie McLaughlin -- bios indicate both use "she" pronouns and are Canadian
This book is not particularly educational about Pride, but it's really fun. It's in part an alphabet book, and each page you can stop and look for more items that start with that letter (if that's enjoyable and developmentally possible for your kid).Interracial family with 2 ~moms, a walking kid (who is lighter skinned), a baby (who is browner), a dog (and a cat, who does not come to the Pride parade).