In reply to Babika:
I will be watching the thread with interest as we are interested in potentially carry-able, strong 4 person tents too (us and the 2 kids anyway). The strong geodesic market is small but includes the Appkit Zhota (3+), the MEC Monadnock, a very expensive Hillelberg, the TNF Bastion 4 and the MHW Trango 4 plus the second-mortgage worthy Terra Firma.
There are a number of lighter models (MSR Pappa Hubba, Elixir 4, etc) that have mostly mesh inner plus lower strength poles, and a group of similarly specced Scandinavian tunnels (Hilleberg Nallo 4 and equivalent) that are lighter if prepared to move away from geodesic (something I'm a bit reluctant to do as really bad weather round here often involves huge shifts in wind direction and good pitches can be hard to find).
Ultimately in your case my suspicion is that you might as well save a whole heap of cash and just buy a car camping tent that doesn't need to be over-specced. There is a lot to be said for being able to stand up in a tent if you are going to be in it for a week or two. We've got an REI Kingdom 8 + Garage that was cheap as chips and is huge (have played cricket with the boys in it when it rains!)
Cheers
b