I saw the Cayenne at the Paris motorshow and at that time I felt the luggage area was large enough. OK it's not huge but it seemed decent to me. I think with one baby it's big enough.

When my 2 daughters were babies we had an A6 Avant (the old shape) and we had not problems to fit everything... I had the impression, the Cayenne's trunk was bigger than my current station wagon (A6 Avant)... May be I'm wrong or I love the Cayenne so much that I'm not partial