For B1 level, you can use EXAM LIFT https://www.cambridgeenglish.org/es/learning-english/games-social/exam-lift/ It’s free and easy to use.
For younger kids SING AND LEARN for level PRE-A1 is very good https://www.cambridgeenglish.org/learning-english/parents-and-children/activities-for-children/sing-and-learn/ and it also provides a pdf with help for parents and the answers to activities. For full information about it and for other levels please see the blog.es info and the links at the bottom of it. And remember that this is only just in case they want to do something at home.