It certainly sounds like these children should be eligible for special educational services in their school district. If that happens, there will be a written Individual Education Plan (IEP) that will outline their strengths and weaknesses as well as goals and objectives for their learning in all areas.
You can certainly work with these children's teachers on supporting the teaching that is going on in school. You can also see if they might be eligible for books on tape after the evaluation has been completed.
In the meantime, the best thing you can do is to read to them about topics that interest them as well as good stories. Once you get to a natural stopping point (after a page, perhaps) talk about what you have read. Encourage them to make predictions about what will happen next. Clarify tricky vocabulary, showing them how they can use context to get clues about the meanings of words. Reinforce these words whenever you can in conversation. When you've finished a chapter, take their dictation of a summary about what they've heard as well as questions that are raised.
You might want to read, What's Wrong with Me? Learning Disabilities at Home and School by Regina Cicci. There are also many websites that offer ideas for parents and professionals working with children with learning problems. In particular, have a look at LD Online and Schwab Learning.