A list of puzzle apps for kids - these will challenge your kids and help them develop critical thinking skills. By solving puzzles, students will be implementing critical thinking and problem solving skills.
Marble Races with a cheap pool noodle (occupies the kids for hours.) Did this, but instead of cutting the pool noodle, the marble is small enough to fit inside the full noodle to roll down. Then can use the noodle for other things too!