Apple's DVD player software lets you change your region code a set number of times (5, I think) and then it's permanent. You should see a dialog box explaining this if you insert a region 1 disc into your iBook.
So you could certainly watch it with your iBook - just remember that you have only a limited number of times to switch back and forth.
On the other hand, if you buy a 2nd, external DVD drive I *think* you can have each one on a different region code.