A few questions about writing Children's books?

[Godessy1]

I want to write a collection of children's book but I'm new to the genre and I tried to research but I have a few unanswered questions:
Word count per story? (I'm thinking of having three stories in one book so three chapters three stories.
I know what the stories should be about but what should the age ratio be? 3 or 5 years and up? or 7-10 years? so that's from year 1 to year 5 (primary school)
Do I draw the pictures myself? because I can draw and I wouldn't mind doing the illustrations?
When I send the manuscript to an agent do I send the pictures along with them. It's my first time writing this genre as I said so HELP! haha thanks. And any other piece of information you know that you think will help, please share...