What it says on the tin, please. I am finding a lot of children's books are either very twee, US-centric (which is fine but we're in the UK), or very in-your-face in the 'Jane's two mummies' style, which seems more sensible for children with straight parents learning about other types of family than for children who have two mummies.
Don't know how old your kids are, but there is a lovely picture book that my kids loved when they were small called 'my favourite places'. It's a NZ book worth very few words, which basically involves a little boy going for a walk and imagining having all sorts of adventures. It finishes with him getting back in time for tea, and the picture shows him in the kitchen with his two mums - no comment on this (not sure I even noticed the first time I read the book), and I really like the fact that it is just completely ordinary and incidental to the story.
with very few words. I know this might not quite full the gap for you, as it really says nothing about this boy's family at all, but I thought it was such a lovely book, and so refreshing to see a gay family represented like this.