Despite the younger offspring's unwillingness to provide details last week, it would seem that they really were studying turtles. This rendering was made with leaves and other plant matter. Also, I learned from the younger offspring that the "tummy" part of a turtle's shell (not shown) is called the plastron.
Elder offspring made the illustration below. The one making the diary entry is the ant, at the lower right. It is possible (though unconfirmed) that the larger animal is a wombat or a bandicoot. Update: The furry animal is a rabbit.
Both of these artworks are beautiful! You have a budding Andy Goldsworthy on top for sure, and there's something very Quentin Blake about the bottom one.