I suggest you provide a lot more information.
'4 DC motors' is not very descriptive.
'4 12VDC 2 Amp motors' would at least clue the people here whether you can have success or not.
Do you want full independent control over the motors?
What kind of inputs come from what outputs on your FrSky Receiver?
And are you going to use an Arduino (this product is a shield).
And, did you not read on the product page 'this board is capable of driving a pair of high-current motors'?
That's a pair - not 4.