are you choosing between a Rockhopper and a Hardrock? I believe the Hardrocks are the only Specialized models left that use A1 (in their mountain-bike range).
For my money, I'd go with the M4 frame and the Rockshox fork. (In fact, I did buy matching, M4 Rockhooper frames last spring for my son and I). I agree with the previous advice about the M4 frame being more upgrade-worthy. And Rockshox is one of the leading fork companies. I'd take a Rockshox over a Suntour any day. In fact, I doubt I'd even buy a bike with a Suntour fork on it. Suntour in my mind is low-end.
It's cool that your kid's school has a mountain-bike club. I had nothing like that growing up.