Parallel Transistors in Constant Current Load
Directly paralleling the transistors is a terrible idea- the threshold voltages of the MOSFETs will be different and one transistor will take much more current than the other- further you are only measuring one current so the total current may be greatly in error. It's worse than with BJTs.

Fortunately op-amps are cheap and you can just use two or more (one per MOSFET), fed from the same control voltage, each fed back from an individual source resistor. Use a single supply op-amp, not an LM741. That way each current will be precisely the desired fraction of the total, and the total will also be accurate. There is no need to match transistors or resistors (but the resistors should be accurate enough for your desired current accuracy). The currents from each transistor will simply add.