Maybe if the tank isnt so big you can temporarily transplant the entire community to a spare tank/tote in a fellow NYC TPT members home with your established filters and some original water.
another option is to talk to a LFS and see if they can keep your fish and feed them now and then for the 3 weeks your gone.
This way you can rest your mind easier, about your faunas caretaking.
I just read this, that is really good to know for my next summer vacation. Thanks!