I'm trying to put together a Christmas card, and I'm thinking of using 3 pics - one from the wedding of H, me, and the 2 kids, one of the 2 kids at camp last summer, and this one from this Halloween:

The wii is my son, the angel is my daughter, and the devil is their stepsister, E. The card will go to people who don't know E, but the halloween picture is so cute I want to use it and while I could crop it to cut out E, she and N purposely went as something together, and it would seem kind of mean to cut her out.
On the other hand, how weird is it to include E when most of the people on my list don't know her?
She calls me her "stepmom," lol, and she's coming over this Friday to spend the night with my kids (mostly to make up for last week, when my ex watched the kids a couple of extra days), so we have a good friendly relationship with her. She and my daughter, obviously, are very very close.
But is it too weird and borderline inappropriate to include a pic of her in our family Christmas card? I'd run it past her mom to see if she had any objections, if I decided to go with it. Thanks for your opinions!