Translation:The two ladybugs are having their lunch in the garden.
"The two ladybugs take their lunch in the garden." seems the best translation to me.
I would go so far as to say that "are having" is just wrong. See https://www.collinsdictionary.com/dictionary/french-english/prendre
Note from a native speaker: Prendre son déjeuner is often used in france for Having breakfast, although the exact expression should be Prendre son petit déjeuner.
For Having lunch, we d rather say: déjeuner.
You will often hear Le "p´tit déj"= the breakfast.
Dé Jeuner literally means to Un fast.