On my Off days I read very simple books that the kids are very familiar with, that way they do ALOT of the actual reading. Nursery rhyme books are good as are fairy tales with repeated lines. Like " and I'll huff, and i'll puff and I'll blow your house down"
I find the trick with the iPad and audio books is in how close you can be while doing it. Climb right into bed with them or snuggle close. Also audio books are only loved by kids who have something to look at too. So definately get the ones with a hard copy book too.
Don't feel any guilt over missing a day hear and there, it's easy to make up for it on your good days. Read through out the day and on your off days play a tweedlewink DVD before bed instead. We did reading first thing in the morning for about 2 years as that fitted better with our moods!