Metaphor examples from poem By Shannon

The poem I'm using is "Nocturne" by Jane Yolen. A beautiful poem with wonderful illustrations. As you can probably tell from the title, the poem itself is about night.

An example line from the poem:

In the night,
in the velvet night,
in the brushstroked bluecoat velvet night,
a big moon balloon floats
over silent trees...

The actual vocabulary in the poem isn't difficult. The book is recommended for ages 4-8 years, but I wasn't sure if it was too soon to require students to think abstractly about figurative language... Any help would be appreciated!!