以下是一些适合三年级下册学生在六一儿童节使用的英语祝福语：

1. Happy Children's Day! Enjoy your special day with family and friends.

3. Have a wonderful Children's Day filled with laughter, joy, and lots of love.

4. May your Children's Day be as bright and colorful as you are. Have a great day!

6. Happy Children's Day to all the little ones! Keep being curious, creative, and imaginative.

7. Sending lots of love and hugs to you on Children's Day. Enjoy your day and make some happy memories.

8. May you grow up happy, healthy, and full of hope and wonder. Happy Children's Day!