Always plan according to the needs of the primary user. This is important so you will know what kind of materials and features you need. A bathroom for children and adult would have different needs and you would use different features, too. For a child's bathroom, use non-skid surfaces and rounded edge to avoid injury. You can also place anti-slip mats. You can have adaptations for disabled persons by having grab rails to walls and close to the toilet. Consider a wall-hung sink so that people who use wheelchairs can move closer to it with ease.
A home would not be a home without a bathroom. The bathroom is a private area for sanitation and comfort. It is a place where one has a private time in taking care of their personal hygiene by taking showers and others. One would always want to feel refreshed and relaxed by the time they leave the area. But of course, a good bathroom that is clean and well-designed would be a better place to clean-up.
Bear in mind that kids are playful and are prone to slipping and bumping into things even if they are in the bathroom. Place safety products in the bathroom like anti-slipping mats and adhesive pads that stick to the bottom of the tub. Also place drain and faucet covers, you can choose covers that are also decorative. Have a cover clamp for your toilet. Just use plain white so that kids will not be curious in peeping into it and be put to danger.