The only homework the boys will have until 4th grade is to have us read aloud to them 15 minutes each day from something above their reading level. But even before this requirement, we've read to them from chapter books. I started with One when he turned 5 and we started Two's first "big book" tonight (Despereaux). Some of the ones we began with that I would recommend are the following:
The Chronicles of Narnia by C.S. Lewis
The Hobbit by Tolkien
The Magic books by Edward Eagar
Despereaux by Kate Dicamillo
Farmer Boy by Laura Ingalls Wilder
Redwall by Brian Jacques
You can also try anything by Edith Nesbit - some kids may like them and some may find them too old-fashioned. I've not actually read them to the boys yet, but One listened to Five Children and It on tape and could not be disturbed - he almost gave up eating until it was finished.
Whatever you do, don't go for the abridged version of anything. If the language is too complex or the subject matter too mature, just wait a year or two. It's much better to expose your kids to the amazing language of classic books than it is to read something just to say you did it.
I also have a very personal opinion that the Harry Potter books should wait until kids can read them themselves. If they're too young to read these books, then they're too young to deal with what's in them. Just a peculiar opinion of mine, and I can't think of any classic children's book I would apply it to. And I don't think the magic in them is really witchcraft or any of that nonsense; I just don't think they're children's books, per se. More like teen books, really. Just my own personal quirk.
Starting this tradition early was really a great decision. This winter One and his dad read all of the real, actual Three Musketeers (all 500+ pages). One was enthralled, and is now a die-hard Dumas fan (his dad's plan, of course). Now they're finishing Robinson Crusoe (they hate it, as it turns out, but are slogging through in hopes that it will help One finish Moby Dick in high school). Next up is either Swiss Family Robinson or Johnny Tremain - it's my turn so I'm lobbying for the latter, but it's up to One.
When I was young I read The Austin Family books by Madeleine L'Engle over and over; one of the things I loved about the family was that they read together every night. Hard stuff - Shakespeare - but they loved it and found it fun. I've always wanted that for my children, and I'm so glad it's working out. We plan to keep this up until homework drives away all semblance of a bedtime routine.
Well, this has been a little disjointed, but the main point is this: chapter books, people, chapter books! Enjoy them!