Everything Joanne says is good. I'd just add that unless you're walking at 3 mph plus (2 miles in 40 minutes or less) on a 10 percent or greater grade, I don't think you need an extra packet.
But, if your alternative packets plus IP don't add up to at least 100 g of protein a day, maybe you can rethink. I suspect that if you keep this up in a couple of weeks, 2 miles will seem like nothing.
Thanks for adopting the dog.