I live in New York also so I completely understand! The best way to let it be known that you prefer gift cards would be word of mouth. Some people are going to want to give you an actual gift so do be sure to list some actual items. Most stores have the option to list gift cards as an item so you'll want to be sure to include it on there.
Remember there is pressure to give large amounts of money on a gift card that some people may not be comfortable with, having actual items of varies amounts give those who want to give some options.
Congratulations and Well Wishes!