Basically everything USMC6177 said, plus this:
I like polycro for ground sheets. I think the weight and performance is similar to tyvek, but it's easier to source locally in small quantities. In any case, forget the shaped footprints.
There are loads of tent options in that price and size range. Just bear in mind that a 2-person backpacking tent will be very, very snug with two adults and a child in it.
I've had 2 Sierra Designs 2-person tents (old Lightning and current Flashlight 2), and I've loved them both. My brother has an MSR Fast Stash, and that's also a neat 2-person shelter.
Here's what I'd do: get both.
You won't want to carry a tent big enough for all 3 while you're on a solo trip, and you won't want to sleep 3 people in a 2-person backpacking tent.
For solo camping: Finish out your hammock setup with a homemade bug net + ridgeline for $20 or so, plus a cheap amazon or woot tarp. The yukon walkabout fly is decent and very cheap, if a bit small. For colder weather, sleep on a pad and make a wind break under-hammock out of a dri ducks poncho.
For family camping: decide if you're really backpacking as a group. If so, haunt Steep and Cheap, Campmor, Woot, etc for a tent. Find one with a separate rain fly so you can make your wife carry half the weight. If you're car camping, just buy a cheap Coleman or whatever for $50.
You'll eventually have a dozen shelters anyway, might as well get started now