I like to start with the game itself, the player behavior, AI and the stage, leaving the menu and other things for end, so, be able to focus in gameplay. Games for kids sometimes ask for a little bit of AI in the behavior, to help them play when they repeat a challenge more than one time, or they will give up easy.
E.g. I had a game where my son was typing, like "Mario teaching type", when the stage was using only single letters, he was well playing, but when it become to throwing some words, he instantly asked me for help, and I recognized the need of an AI to help him if he miss some letters of the words, so, when he type a word missing one or two letters, the AI will simple bold the missing letters and ask him to type them in the end.
Another sample was in a jump game like Mario, he fell of the platform while jumping by two times, and I did an AI to help him in the third try, so, when he pressed the jump, it was too late, but the AI recognized the edge and jumped before, confirming the jump button with a delay by using a condition listening with a gap of time to happen =]
Kids are awesome and they deserve more attention, but today games are hard, bad explained and bad oriented in many ways, throwing different types of gameplays without even introducing a world or telling the player what is happening and what the game expect to the player, what objective and reward it will give.
Your game sounds amazing and certainly will introduce kids to the Science by teaching them about gravity, speed, acceleration and the most important, with a nice reward when finishing it with your animations.