Hello Mr. Gray,
I have been developing games with Unity professionally for over three years now. I think that your best bet if you want a game for 3-10 year olds is to apply your artwork and story to an existing game style, like a Memory, Match-3, Flappy Bird, Jigsaw Puzzle, or some such thing that could be easily retooled for your characters. This would allow you to have a proven game style at a fraction of the development cost. I would be happy to discuss with you what kind of game you think would be best and how best to integrate your characters into it, so please contact me!