There's barely any traffic - its a four lane road but it only services the gated community of Ko Olina, which is small. Its not a far walk, but if you are carrying heavy grocery bags, it may be long and you'd be going up-hill up the Aulani driveway on the way back. If you look at the aerial image of Aulani on Google Maps, you can see the length of the driveway and the walk over to the Island Country Market.
I agree with PPs that you should not mistake the Island Country Market for a grocery store. IMO, its akin to a 7-11 or similar convenience store. As others have noted, they have basic toiletries, snacks, some drinks, a small prepared food section, and souvenirs. The prices are high and reflective of what you'd expect in an area that was curated and targeted at tourists. If you just want snacks, some drinks, and some basic breakfast type items then I think it would be sufficient, but you need to do a week's worth of grocery shopping for meals, I'd suggest taking an Uber to Walmart or Safeway in Kapolei. Also, depending on when you're going, the satellite rental car offices in Ko Olina could be open by then so you could also consider doing a one day car rental to take care of your groceries and anything else you may want to do. Alamo operates out of Aulani and Enterprise operates out of the Marriott next door, but I believe both are still closed in the current environment.