Genevieve, I also have this thread going, but it's specifically focused on car camping tents, http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=19572 , because my wife and I already have a backpacking mountaineering tent (for winter and higher elevation) and are about to pick up a lightweight Tarptent to replace a heavier older backpacking tent.
Let me second comments that you can take your kids backpacking right now, and it would be easy to pick up a nice roomy Tarptent large enough for all of you.
Note that I have cousins who hiked while pregant until a few weeks before they gave birth, and raised their kids backpacking from an early age. I didn't start backpacking until Cub Scouts at age 7-8, but my family took me hiking even before I could walk. Backpacking teaches so many valuable skills and lessons being lost in generations raised on instant-gratification tv, internet, etc.
There are some good resources on this site, other sites and in books on backpacking with kids. Highly recommend you search this site.
Also, my wife and I are also going to pick up a Tarptent and are just trying to decide between the models. We've been looking in particular at the Rainshadow 2 (very roomy), Double Rainbow (2 doors, bit stronger than Rainshadow 2 but less space) and Scarp 2 (stronger than Double Rainbow and Rainshadow 2, size similar to Double Rainbow).