I get worried that I'm wearing out my battery as it goes to two bars, and the engine kicks in, and we're there parked for over an hour waiting for Mommy to finish at the mall with the engine on and off. If I'm doing this all summer, any consequences for battery life or engine life? Of course mileage suffers, but it's better than dragging tired kids into the mall.
Yes, that puts some (minimal) wear and tear in battery, but this is what the car is for. If you are concerned about, just walk instead.
The car will maintain battery levels that increase the longevity of your battery in the best way possible. Sure this will add extra wear on the battery and it depends on how often you do it. I doubt this is any worse than just normal driving as the car constantly uses and drains the battery this way as well (even if your S.O.C. reading is steady). The car won't let you drain the battery to a degree that will accelerate damage to the battery.
Has to be better options than to sit in the parking lot for over an hour. Drive to a nearby park and let the kids do something active.