WDW room cooler: safe for simple breakfasts, or stick to shelf-stable?

Planning our first on-property WDW trip and trying to keep food costs down without making everyone miserable.

I keep seeing mentions of the in-room beverage cooler. If you've actually used it, is it cold enough to safely hold basic breakfast stuff for a few days (yogurt, cheese sticks, hard-boiled eggs, cut fruit), or is it more "just a bit cool" and not something to trust with perishables?

We're coming from Ontario so I'm used to packing snacks for long travel days, but I know we can get disorganized once we arrive and end up buying breakfast in the parks every morning. I'm trying to make a realistic plan that doesn't waste food or money.

If the cooler is not reliable, what are your go-to budget breakfasts that work in a typical Disney room? We'll have a couple picky eaters and mornings are usually the hardest time to get everyone moving, so easy and quick ideas are ideal.

Bonus question: do most people do a grocery delivery to the resort, or just grab a few things from the resort shop and accept the markup?

Not trying to break any rules, just trying to avoid food going bad and blowing the budget. Thanks!