No. PWM doesn't work through a shift register. (At least not easily...)
Why? Ive seen some tuturials using shiftpwm arduino library. "ShiftPWM is a library for Arduino to control many PWM outputs using shift registers (for example 74HC595). "
And about the FET, will this one http://www.mixtronica.com/electronica-componentes-electronicos-semicondutores-transistores/3759-ap2306agn-hf-3tr-mosfet-n-30v-0-035-ohm-sot23-ap2306agn.html, do the same as A0I514?
Transistor Polarity: N Channel
Continuous Drain Current Id: 5A
Drain Source Voltage Vds: 30V
On Resistance Rds(on): 0.035ohm
Rds(on) Test Voltage Vgs: 4.5V
Threshold Voltage Vgs: 300mV
Power Dissipation Pd: 1.38W
Operating Temperature Min: -55??C
Operating Temperature Max: 150°C
Transistor Case Style: SOT-23
No. of Pins: 3
MSL: MSL 3 - 168 hours.
5A more than enought for what the colour channels ask for right? 4,5 Vgs and low Rds.