Keeping kid's attention on what they are reading is often a matter of whether or not they are interested in either "reading" or in the subject that they are reading.  One way to improve their attention span is to build on a previous lesson.  If your kids responded to a particular lesson taught, then structure your reading lesson to relate back to the previous one.  A fun activity that relates to the reading that they are about to begin can peak their interest, such as a humorous poem that relates to the short story that will be read next.  
Ask yourself why would the kids want to read this.  If you can figure out that answer, then you can plan your lesson accordingly and convey that benefit to them.  Kids are often not good with delayed gratification.  If they must wait a year to benefit from the lesson, then it is not worth is.  Don't forget that kids are people too.  We all have the same basic needs, we all want to know "what will we get in return for our attention".

Well u gotta look at it this way. Did u like to read when you were younger. I didn't at first. But i'm now 19 years old and I love to read. See what the kids are interested in. You will see how well they adjust to the reading. I have a 4 year old cousin and he can read so well for his age. He is in preschool and he can practically read a whole book by himself. You just gotta take it step by step with the kids. Read with them. Help them sound out words. Put them in groups and ask them to read to you. That will tell you where there lacking in. That way you can help them knowing what they need help on. if they don't understand what they are reading ask them questions or explain it to them and give them better ways of figuring it out themselves.

I suggest the Phillip Roy Academy Online. A lot of kids are very interested in computers and using computers. They have a great academic program. I use the pre-k program with my daughter and she stays very well focused through-out the activities with me. Check it out and I hope this helps!

Good luck!

How about MP3 audiobooks?  I use them in my middle school reading group and the boys especially are drawn to the integration of technology in the classroom.  Plus, the books I use are sports-based books that tell the stories of real kids who play football, baseball, skateboard, etc.  My students are really into the texts, and the audio portion of the program has definitely improved their vocabulary use and retention.

When we read we should be making pictures in our minds.  Some children with decreased reading comprehension have difficulty visualizing what they are reading.  Are the children you are concerned about able to describe the characters in the story?  Can you ask them questions to see if they are "picturing" the story as they or you read it to them?  www.lindamoodbell.com offers suggestions and products to help with reading comprehension using methods to increase a child's ability to visualize.  Hope this helps!