You have 3 kids under 5 years of age?
Stick with picture books for them.
If you have some older kids (like 10 or 12 years of age) you can buy kindle4 non touch (70$ model) and make it a personal present for them. No sharing with younger siblings. Its only theirs. I'm saying this because there was nothing more precious and enjoyable to me then reading books when I was about 10-11 years old. Even if your older kids dont like reading they might give it a go if you make it only theirs. Kids want certain autonomy at that age and sense that they are important. 10/12 year olds dont really want to be around 3 toddlers under 5 years. They would be rather cooped up in their room reading Harry Potter or Hunger Games. So make this kindle a present to them. They will appreciate it. And toddlers would prefer a picture book they can drool and draw on then having to sit quietly and read.