OP mentioned that the kids had NEVER ridden before.
Most 120's are pint sized ... the Snow Scoot / Sno Sports are 2/3 size machines. Our Sports are as fast as the 250 cc bravos which is plenty fast for kids. The riding positions was waaaayyyy ahead of its time and is real close to the position on most new chassis. With a long track & plastic skis its hard to believe that that they are 20+ year old 125 cc sleds!
I know. And a 120 is a waste for a kid that old. Snow scoots are great but they are few and far between. Also they are not cheap either.
Like your last post said, it all depends on the kid, but I reccomended 250-340 size machines. Doesn't get much smaller than that.