Diapers & Bathroom Situation:
In the parks, I use these bags as mini diaper bags. My personal preference is to not lug huge backpacks or diaper bags into the bathrooms. These bags are a perfect size to hold diapers, wipes, clothes, diaper cream, etc.
When you're potty training, or potty trained, I've used these to hold the toddler seat for toilets, sanitizer wipes, and/or toilet covers. Since there are two, waterproof pockets, you can keep the toilet seat in the large pocket, and the sanitizing items in the small pocket. Use the toilet covers provided in the bathroom before placing the toddler toilet seat on to help keep things clean.
If you're thinking this is all too much, you are the lucky ones who have never experienced a toddler absolutely refusing to use a public restroom because the toilets are scary and they need a potty seat!
Disney Baby Care Centers: Don't skip the baby centers! These are located in all parks and have changing tables, bathrooms, bottle warmers, microwaves, seating, water fountains, etc. These centers offer a quiet place to change a diaper, change clothes, eat, etc. They also have a few supplies for sale if you forgot/run out of diapers, wipes, rash cream, etc.