B&H will help fine. Tell her to go upstairs and get in the queue for an assistant over on the right hand side (there are 50+ assistant desks!) - she tell them what you want, you'll be presented with a receipt. Go downstairs and pay (note there are different kiosks for card and cash), then move on to the pick up. Its a really efficient system!
Tax in NY is 8.8% if I remember correctly.
Tell her to look around for a small card for B&H or in one of the freebie guidebooks in the hotel lobby, it will entitle you to a free gift ($50 dollar spend or over) - I got a small rucksack, nothing amazing but could come in handy!
To get there walk south from Times Square on Broadway, when you get to Macys (its kinda hard to miss) turn right down 34th, walk to 9th Ave, B&H are on the opposite side of the road on the corner of 34th & 9th - look for the green window shades.
The other place is Adorama, I didn't go there, but they are at:
Adorama Store, 42 West 18th Street, New York City, NY 10011.
Thats quite a way downtown between 5th & 6th Ave.