once i have been published, then what?

[Pascha]

Once your book is published you will need to work hard to promote it, especially if it's your first.
Try local radio shows and current affairs shows.
Go to as many book stores as you can and offer book signing days, unfortunately, if you aren't already known, you probably wont get many people turning up, but do it anyway. Also, once the signing is over, offer to sign another 20 or so books for the retailer, this way, they can sell the books for slightly more and you can offer the signed books under the proviso that they must be displayed in an obvious spce, this you are more likely to sell more.
As soon as you have exhausted your own attempts at publicity you can start on your next book, they beauty is, once you have had one thing published, you will find it a lot easier to get you next work out there.
I don't know where you are, but in Australia, every book that is published must have at least one copy sent to the national archives. This will give libraries the chance to pick up your books too.
If it is a children s book (as you indicated) you can go to your local libraries as well and offer to do a reading for the children on certain days. You may even sell a few more copies this way.

Just remember that when it comes to publicity, the publisher usually doesn't put in the time deserved for your efforts, obviously becasue they are very busy. So it will almost always be up to you to make your work successful.