I would be that you could add the bulk of the small fish (blennies, cardinals) in one shot no big deal. I'd wait on the mandarin until you're positive you can sustain the food source. After that, if it were me, I'd add one of the big fish at a time (wrasses and hogfish).
And as for sand sifters, I have a yasha hase goby, and it's pretty easily my favorite tank inhabitant. He hides 50% of the time, but is so freakin cool that its worth it.