So you want individual control, ie 4A for each MOSFET, those Sparkfun ones are OK, but overkill on
the 60V rating, 30V MOSFETs have lower on-resistance.
0.05ohm x 4^2 = 0.8W per MOSFET, so a small heatsink is indicated. Get some 10 milliohm 30V
MOSFETs and no heatsinking needed.
To switch all of them together is 20A which is beyond those MOSFETs as I said earlier, <=5 milliohm is
a good figure for that, a bit harder to find as logic-level, but they exist down to about 2 milliohm last
time I checked.