My son last year was about the same size as your son.....just over 5'2" and 110 lbs. He rode a Kessler stock 180 with an Apex Plate and f2 titanium bindings. But he is a really aggressive rider and could get the proper flex out of this setup. The year before he had a Custom Coiler 156 SL board and a Custom Coiler 172 New School Race board. These were designed with more flex as he was barely 100lbs that year.
This year he is 5'6" 120lbs and is riding a custom Kessler 180 about the flex of what the woman world cup riders have with an Apex plate. He has a 159 Custom Kessler SL this board is pretty stiff but he wanted the shorter length. He is riding a K Plate on this board. He has UPZ boots.
The moral of the story is that between 12-15 boys grow and change a lot......so whatever you buy this year may not be the equipment he needs next year to be competitive.
The Coilers are great boards. Less then $800 custom fitted. Riley won a silver in the GS in the breaker boys on this board and was the U15 Canadian National Champion. Great board for racing USASA and Jr. races. Not quite what you need to race FIS and NorAms.
Custom Kesslers are expensive and right now may be hard to get given it is an Olympic year. There are some used ones floating around. If you want a 174 barely used Kessler in mint condition for $850 contact. Desiree desireelabrecque@mac.com It was designed for a female rider and would be more forgiving then a stock Kessler 171
I recommend UPZ boots. They have one more buckle then the Deelux boots and hold smaller ankles in place better. Worth spending the money to get these boots.
Here is the contacts/websites for various equipment
http://www.yyzcanuck.com/
The contact at YYZ is Andrea - They stock Deelux boots, F2 bindings and F2 and Donak boards. The f2 bindings are world cup standards
http://www.apexsport.ca/
Apex distributes Kessler boards and Apex and Kessler plates. The contact at Apex Sport is Henry Kim. Apex Race Plate combined with a Kessler Snowboard is one of the world cup standard configuration for GS racing. Andris Pommager the Overall World Cup winner in Alpine Racing is a pro rider for Apex/Kessler. Of course there is pretty hefty price tag for this equipment.
http://www.coiler.com/home.html
Bruce Varsava is the sole guy behind Coiler boards. There are a good snowboard. Custom made to the rider and more reasonably priced then a Kessler board.
http://www.upzboots.com/
Dan Yoja is the contact at UPZ boots. These are the boots used by most riders at the world cup and NorAm level.
There are other boards SG (Sigi Grabner), Donak, Jasey Jay. all used by various world cup riders.
The good news.......there is quite a market for used race equipment. Especially the smaller stuff. So even if you have to buy brand new, you can likely recover 40-60% of the cost if the equipment is in good shape on resale.
Hope this helps.