Those coaches who have bookmarked your son will see when there are updates.
As to the remark about which schools use the site that is somewhat immaterial if the reason you are using the site is as a storage point for info, pics, and video for which you supply the link to any coach you are trying to interest in taking a look at you.
Important point is to list your HS and Travel Coach info so the coach looking in can make a call and get an allegedly trustworthy reference before taking a look.
These sites are probably the lowest priority of all your recruiting efforts, again other than as a storage and easily accessed web point, with much higher priorities being a couple showcase appearances, targeted college camp appearances,tournament appearances in front of a college coach for a school you ARE interested in, and direct phone calls to coaches you are interested in.
Regardless of the division level these sites are still a tool more for you than for randomly wandering college coaches. So as to your stats question, sure update it. Not sure how valuable career stats of a teenager are so what we do is keep the current "season' stats reflecting the following 4 seasons: Exhibition/Non League HS, League HS, Travel/Legion, and Fall. The 'career' stats reflect the accumulation of the current 'year's' season. And we note that in the comment area.
Again, its a storage tool. I wouldn't annoy coaches with every change. Perhaps more proactive as a 2013 might be a quarterly note saying you remain interested in XYZ and if they want to see more have them click on your link to the recruiting site. Once rising senior year summer rolls around, you could switch to monthly, but again keep it focused on your changing list of schools you have selected based on Academics, Social Atmosphere, and Sports which, IMHO, is the order you should prioritize.