I wish I could help you more, but here are a couple links and steps that may help advance your progress.
The large and well-known publishing houses deal almost exclusively with agents, and many simply will not look at a proposal that is not submitted by an agent. You have to realize that the average house is dealing with an overwhelming number of submission s. One of an editor's main jobs is to keep in close contact with a group of agents, letting them know what kind of books that editor is looking for, and getting them used to that editor's taste.
Ideally, a good agent will help you put the final polish on your proposal, and will get it directly to the editors and publishers most likely to buy your kind of book and most likely to publish such a book successfully.
1) Find agent's for children's book writers
2) Submit your book proposal to as many agents in your genre as possible
3) Let your agent guide you to the publishers that are most likely to buy your book
Check out for agents and publishing houses: http://www.literarymarketplace.com/lmp/us/index_us.asp
Your proposal should include:
Be clear, articulate and to the point. You would be surprised how poorly presented and poorly written, many proposals are. The same rules apply as with anything else in life: this is your sales presentation. Go all out to capture the buyer's interest as quickly as possible, and hold it for as long as you can. How your proposal looks, and how professionally it is presented, is critical to shaping the attitude with which your proposal will be viewed. As a general rule, you should include the following:
1) A one-page cover letter
2) An introduction that sells your idea in two pages or less. Pretend that you are writing the publisher's catalog copy for them; tell them what the book is about, what makes it unique, what the market it is for your book, and how it will be reached. The more concrete you are, the more convincing you will be.
3) A table of contents, annotated if necessary, to give an overall picture of your book.
4) Sample material, enough to convince, and enough to give a sense of what they are buying.
5) Information about the author--what makes you the right person to do this book.
6) Marketing information and plans. How can you help sell this book, what special places and ways can it be sold, and what special ways can it be promoted.