I'm not a teacher, but I have friends who are.
You know, this is a sticky situation.
With so many blended families, kids being raised by aunts and uncles or grandmas and grandpas, there just is really no way for a teacher to get into who the gift is made or intended for or worrying about if they don't make at least two of something, somebody will feel left out. It's just not possible. And I know for a fact that funding for so many things have been cut to the extent that teachers often spend their own money for the little craft projects that kids make for these things. It's just not possible to make everybody happy.
I know of one little kid who made something and he wanted it specifically to be given to his mother. Well, he didn't live with his mother, hadn't seen her in quite some time, and his "step" mother was quite offended because after all, SHE was the one who took him to school every day and picked him up, SHE was the one who took treats to class and did everything for him....SHE was his mother. I could see her point to an extent, but, it seemed kind of immature to me, and it certainly wasn't the teacher's place to tell the little boy who the gift should have been intended for. He wasn't having a melt down about it, it was the step mom.
Step parents are no doubt very important and integral to children's lives, but as far as teachers taking the "extra step".....take a good look at how many kids are in each of your children's classes and consider how many of them have more than one family and then add up the time and expense it would take for each of those kids to make something for everyone. Then add in the questions from the other kids about why someone gets to make more than one thing. I don't think it's intentional rudeness on the part of any teacher to just have each kid make one thing.
My kids have made things for Mother's Day and wanted to give it to my mom. I was totally fine with it. It was part of my gift to her.
Adults are adults. At least we should be. The classroom isn't the place for familial political correctness on top of everything else.
It sounds like you all have great relationships between the adults in your blended family and you should be really glad about that. You can have fun with the kids at home making cards or even taking ideas from the class craft and making more than one to give to other people or keep for yourself.
Just have a wonderful Mother's Day and Father's Day and know that your kids all love you.