Agree with The_Beast, it's exactly how it should be done.
I have 7 in mine - 2 front sucking in, 2 side sucking in, 2 back blowing out, 1 top blowing out.
What you need to think about are filters in front of the fans sucking in. Ideally the case will have them, but if not you could do with making your own. I have to clean mine out weekly, dread to think what the state of my case would be without them.