To make it family - friendly, emphasize their friendship. Have them participate in a sports tournament together. Goku shows off his physical prowess, and Launch uses her wits. They support each other, cheer each other on, and learn valuable lessons about teamwork and fair play. This way, it can be enjoyed by all ages without any concerns about inappropriate themes.
You can focus on their adventures. For example, they could team up to find a magical item that has been lost. Along the way, they encounter various friendly creatures and face some challenges that require both Goku's strength and Launch's cleverness to overcome. There's no need for any inappropriate content, just good - hearted, exciting adventures.
Make it a story about them helping a community. Goku and Launch could come across a village that is in trouble due to a natural disaster or some evil force threatening it. They use their unique abilities to rebuild the village and protect it. Their relationship can be based on mutual respect and the shared goal of making the community a better place, which is a great family - friendly concept.