Perhaps an alternative approach would be to productive some of your prototypes. For example, have you made a cool exhibit for a children’s museum? If so can you make it generic for all children museums?
I think that a great children's museum exhibit would be really interactive and engaging. So if there's an exciting exhibit, I'd think there would be interest in smaller educational projects the kids and their parents could put together. So the OP could also offer to design related educational toys that the museum could sell in their shop, or the OP could sell on his site. At the very least, he could have free instructional videos on his site related to his educational exhibits.