Outer shell for son

Marmot Precip comes to mind. The shell over down for active use may be overkill unless you are in very cold conditions (which won't be wet). The down/shell combo would be fine for rest stops and camp. A shell plus a fleece would be my choice for more active stuff.

There are all kinds of 2.5 layer rain shells. LL Bean, REI, Cabela and others have their house brands that would work. With a kid that age and growing, getting more that a couple years use would be a surprise. I would buy what is on sale.

What size does he wear?

The Patagonia jacket is 14/16 and fits him great. So any lined thick rain jacket shell will be fine? 2.5 is that the thickness of the material? I am looking for used if I know exactly what in looking for. Luckily I have a 9yr son also that can wear it in a couple of years.
Thanks for the help.
Scott

Do a google search on rain gear fabrics to get it all, but the "2.5" refers to the fabric layers and that is a typical lightweight rain shell construction. One layer being the nylon shell, the next layer is the waterproof breathable membrane coated on the inside, and the ".5" is the printed protective over layer to help extend the life of the membrane. A 3-layer shell has a fabric layer bonded over the inside of the membrane, adding expense, weight and stiffness.

http://www.rei.com/learn/expert-advice/rainwear.html has some good illustrations.