Even a logic level mosfet might not be enough since R7 will lower the output voltage of the digital IO. I would recommend a logic level to mosfet gate driver IC under all circumstances since it also protects the digital IO from any signal spikes coming back through the mosfet gate.
Ok, now, if you don't want the gate driver IC, for my LED lighting projects, I use the BSS806N H6327 as it is cheap and switches on completely at 5 Vgs. I would remove R7 to ensure that you get the full 5v when the output goes high, or, if you need a default off during tristate, I would make it something like 1Meg.
Now, IRF520 is beefy for 2 leds and you are working with 12v, if you need more amps, I would use something like a DMN2028USS, also cheap, but more than 8 amps.