halfnote:
...however, I'd prefer that 1 random LED turn ON rather than 2 random LEDs turning off.
How many milliseconds do you think it would take to turn them all off, and then randomly lite one of them?
Answer: unnoticeable to human perception.
Either way is the same, unless you may be getting graded on following the instructions, then that are not the same.
Also, how many times does setup() run?