We have started reading a children’s version at home and our son is loving it, our daughter not so much. I have had to stop and explain some bits as they don’t have the vocabulary for some of the concepts that come up. But we are doing well, it is a great exercise to see what is missing and great exposure to vocabulary we don’t use regularly at home. If you want to get your own version for kids in Spanish your best bet is to go to amazon.es, there is also a kindle version in Spanish in amazon uk which is quite cool since the chapters are written in comic format. The one we are reading at home is published by Susaeta and is a good balance of writing and pictures for our 5 and 7 year olds; if you are not sure what to buy you can look at what guiadelniño.com recommends and to get started today, go to this great site which has Poems in Spanish for all sorts of famous characters and situations. Here is a link to the poems about El Quijote and its wonderful people.
Of course the other option for the culture factor is to get the children to read it themselves in English, Usborne has published a young readers version of it.