The shops and dining inside/attached to the casino complexes will be open most days (esp weekends). May be part of their contracts with the hotel/casino operation, the hours and days they are required to be opened.
Many people believe that Atlantic City Boardwalk is a walkable place with endless shops. No. There are long expanses where the older hotels and buildings were destroyed and torn down - fires, hurricanes, rotten roofs causing damage beyond repair, lack of parking & lack of cash customers, etc. Even the number of rolling carts (where customers ride and are pushed down the Boardwalk) have visually deceased.
I have had my elderly aunt down there twice .... she was disappointed and the casino shops & dining are too noisy ... hard to her to hear conversation. And walking anywhere was both difficult on the 'boards' and too long for the few shops that were open. And the 'open' distances made it boring and too long of a walk to 'the next place'. She has no interest in going back to Skyline Towers any more ... will go to Williamsburg (and too far and not of interest to me) or Wyndham Midtown in NYC (most likely our next trip again).