Hi,
I would check on that MOSFET, I don't think it is a logic level MOSFET, that is it will not turn fully ON with only 5V of gate to source voltage.
I would be putting a fuse in the high current power line to act as protection.
Prototype boards will not take that sort of current and you will need some decent size wiring for the 24V power circuit.
Place a 10K resistor between gate and source to prevent the MOSFET turning ON due to stray current and during the bootup of the UNO.
Tom... 
EDIT: Beat me to it, I'm off to bed, goodnight Grumpy_Mike. 