Let the event supply the subject
Cambridge English’s diary guidance describes different support for different ages. For younger children, a parent can help put an event into English while the child draws. Older children can discuss ideas and write with more independence.
Choose one moment rather than asking for an account of the whole day. You and your child should both know what the sentence is trying to say.
An example page
If you planted beans together, a page might contain a drawing of the pot and the sentence “We planted beans.” This is an example, not a sentence every child should be able to write.
A parent might write the sentence after a conversation. Another child might copy it, fill in a word or write their own version. Label the help in your private notes so that a copied sentence is not mistaken for independent writing.
Read it together later
Ask your child to tell you about the picture. They may remember details that are not in the sentence. You can add a spoken description without requiring another written paragraph.
Keep the original page if you make a later version. Comparing the two may help you choose the next task, but a single page is not a writing assessment. Look at the specific work: selecting words, forming letters, spelling or building a sentence.
The diary can remain a private family notebook. There is no need to publish it to make the activity useful. If you want to add a recording, see digital English practice.