For eating, there is probably going to be no issue. If there is anything it is a plate sharing charge of a few bucks and this is always printed on the menu.
For shopping with cost in mind, stop in Daffy*s for great bargains (they are a chain so there are multiple stores).
Daffy's High Fashion. Low Prices. :: Home Page
Also, Loehman's is great for deals.
loehmans.com
Since everything is decorated for the holidays you can't pass up Macy*s Herald's Sqaure where some of the escalators are the original wood escalators from way back in the day.
Also, you will likely go down 5th avenue to see the window displays, etc. you will see Saks (across the street from Rock Center), Tiffany*s, etc. right in the same 10 blocks (5th Avenue at 58th down to 48th).
If you are still in the mood for bargains, H&M's flagship store is on 5th avenue in this vicinity as well as Zara. Fun shopping at both.
Have a wonderful time!!! You are going to love it.