i don't think you have provided enough information about your motors for us to properly decide whether your mower will be geared properly.
what is the RPM of your motor unloaded at 24V?
do you know the torque?
my hunch would be that you are going to need a lower gear ratio than 11/56 for 10 inch wheels but i can't really be sure without knowing more about your motor.
these motors will definitely work if you gear them low enough but obviously that affects the speed.
what is your desired top speed?
for speed controllers, etc.
you might want to look at web pages specialising in robot wars style battlebots.
the people building those often have the need for high power motors like you plan to use.
also, these guys are building some pretty heavy RC projects: http://www.rctankcombat.com/