This introductory class is about generating interest in the piano. We do not set practise times at this level. Rather, the students should practise as much as they wish. However, keeping the class content alive in their mind is helped by engaging in practise even for a few minutes once or twice each day. This helps the student to make sense of the class content.
So ‘little and often each day’ is a good approach at this stage. Being able to do each task helps the whole class to make progress at a good pace.