The Grand Trunk Ultra Light(GTUL) should make a good starter hammock. Most move on to something different, like a bridge, Warbonnet Blackbird, Switchback, or a longer/wider DIY, but not always. If you do move on it would be around the time your son would need a hammock anyways. The GTUL should tell you all you need to know about hammocking.
I have found that the webbing with cinch buckles like these are the best for me; http://arrowheadequipment.webs.com/a...s/show/2575054
. Except if you're going ultra light, you may want to search whoopie slings.
I start feeling cool at 65F-70F without some instrumentation under me. If you're looking to be frugal, use your pad and sleeping bag(as a top quilt) that you already own for ground use, in your hammock,. You will also need a tarp.