Your cover letter already has a strong foundation! Here's a confident conclusion you can use to wrap it up effectively while thanking the reader for their time:
I am excited about the opportunity to contribute to Growing Kids as a paid intern and believe that my passion for childcare, along with my skills and values, will enable me to make a meaningful impact within your team. Thank you for considering my application. I look forward to the possibility of discussing how I can support Growing Kids and contribute to its mission.
Sincerely,
[Your Name]
Feel free to adjust any part of it to better match your personal style or preference!