You should be able to do most of Naxx with no problems. However, you will not be able to do Thaddius. You will probably have to have tank-capable pets for some of the bosses. Four horsemen will be interesting too, but if you split your team into four parts you might could do it. You'll have to burn Maex pretty fast to avid having everyone webbed. Yeah, as I think about it, there will probably be some significant challenges.

Let us know how it goes.