Has anyone ever used PackIt or similar freeze-able lunch bags? Do they actually prolong the amount of time food stays safe to eat(as opposed to a typical SkipHop/PBKids lunch bag with an ice pack)?

My kids are at day amp, and their lunches sit outside in the heat for 3-4 hours - our typical lunch boxes really won’t keep much of anything cold enough (yogurt, deli meats, cheeses), and it is really limiting their lunch options! Thanks.