What are the most critical factors to consider when choosing kids MTB clothing that balances safety and comfort, and how do different materials, designs, and features impact their overall riding experience? For instance, are there specific types of padding or protective elements that are more effective in preventing injuries, and how do they affect the garments breathability and mobility? Additionally, what role do factors like fit, flexibility, and adjustability play in ensuring kids can move freely and focus on their riding technique, rather than being restricted by their clothing? Are there any emerging trends or innovations in kids MTB clothing that are worth exploring, and how can parents and coaches strike the right balance between safety, comfort, and style when selecting gear for young riders?