Your son will be happier with an A5 because of the cyclone feed alone. Also, there are MANY, MANY more ups and custom options you can add to gun to fit his style of play.
A lightweight hammer is almost a must for these guns. Significantly reduces the amount of kick, make it quieter, and ups your efficiency.
Empire Trracer: Custom on/off bottomline
Tippmann SL-68 II: J&J Ceramic
Tippmann TiPX: Voided Warranty, BK Bolt, Remote line
DP Rev-I: TechT L7 Bolt Engine, Dye Hyper 3 reg
PE Geo+: GR2, GST, Violent Series trigger
Ninja Straightline Remote