Planning ahead is very helpful. If possible, know where the bathrooms are located so you don’t have to search for them when you need them.
Think about the clothes your parent is wearing those days and make sure they are easy to take off in a public bathroom.
If you have established a routine about times of day and how you handle toiletling at home, try to stick to that as much as possible when you’re out.
Be sensitive. Embarrassment can make the toileting experience even more difficult.