If you don't want to deal with publishers, then become your own source of marketing. Build a website and utilize SEO to start bringing in traffic. Make sure you post frequently on that website about topics that have to do with your niche.
Then you can write an eBook and sell that since many children nowadays have tablets or mobile devices. There are also places you can work with that will let you create a physical book. The noted site can also help you self publish eBooks. The hardest part is getting the word out about it, but through marketing online it's mostly a matter of time.
1 - http://www.wikihow.com/Make-a-Website-Using-Wordpress
2 - https://www.lulu.com/