It's a nice idea...reads like some traditional stories. But in all honesty I think there are some problems with it.
The terms "Daddy monkeys" and "Mummy monkeys" are too impersonal to start a story off with.
In order to feel engaged with the tale, the reader (or listner) need to have an interest in the characters from the word go...so what might work better would be to have Pongo discover the lack of food right away.
Also bear in mind the age group of your readers. 2-5 is essentially a group who prefer picture books with much less text.
There are exceptions of course, but in general children this age need very engaging illustrations and fun, punchy language.
I'm a writer...not of children's books but I do have an idea of what sells. If you were thinking of looking for an agent I thinkyou need to work some more on it.