First, read How do I post a question effectively? and Writeup Formatting Tips - your question would be much easier to read with >code< tags.

As for your question, I found The Perl hash How-To very informative back when I found hashes & hashrefs confusing. Since children is an array, you should be able to just iterate over it with a foreach and perform any action that needs to be taken on each child, and increment a counter to count. Also, you can refer to an array in scalar context to get a count.