Hi and welcome to the forum Dollo ...
First thing is yes the Mac.....
As for software or Apps when you buy a new Mac you will get the
iLife 11 Suite and within that you will get iPhoto11 iMovie11 and Garageband. All awesome Apps and being only been out within the last few months it is the latest and have made some major advancements in all Apps.
I know i will have people to back me, but if he only just starting out, it is my belief the
iMovie 11 part of the Suite will be ample for him to start out with video editing and such.
The Mac comes with so many great Apps and its one thing to look at when you do 1st get it. As we can do photo editing in our simple basic Preview
Anyways
As for the Mac.
Do you want portability ?? If not then the iMac is the way to go, and ANY iMac and its specs will be sufficient for any light/medium video editing. So will suit your son.
If you want portability and to do the job, i would have to recommend the 15" i5 MBP. They have good screen real-estate and the Specs again will be sufficient for what he wants to do.
I would even go as far as saying the 13" MBP (which i own) would do the job. The only pitfall of the 13" is the size of the screen. I personally love it, but it still does pack a punch when it comes to computing though ...
I really comes down to it, RAM and Processor speed when it comes to specs ..... The more RAM the smoother and quicker everything will work and the Processor speaks for itself.
Not sure where you live, but when considering buying from Online Store, dont forget to check out the
Refurb Store as you get a refurb Mac with the same warranty as a new machine. And most of these are new ... Something to keep in mind.
Hope it helps some but post back if you have more queries
Cheers
EDIT : If you want to upgrade RAM and HD's DONT DONT DONT get them to do it when you spec the machine through , as they charge ridiculous amounts. Go to
OWC ~ MacSales and put in Mac specs and they will show you all compatible HD's and RAM for your machine. Good prices and quality tested