This year, we'll be taking our soon-to-be 3 yr old daughter on her first real backpacking experience. We tried squeezing into our Lunar Duo today outside–a bit of a tight squeeze.
The only shelter I can find that has a reasonable weight is the Tarptent Rainshadow 2:
http://www.tarptent.com/rainshadow2.html
It's a pity they don't make it in a lighter fabric like cuben fiber. My Lunar Duo weighs in at 42 oz including everything–2 oz polycro groundsheet, stuff sack, and 6 stakes. If at all possible, I'd like to stay around that weight.
I have thought about going with a floorless shelter (maybe one from HyperMountainGear?), but I'm not sure if we'll be OK with bugs or not. We do the majority of our trips in Colorado high mountains in the summer.

