Depends on your area or location. Lower income area suggests that keeping coins is the better option.
By self-serve do you mean unattended or semi-unattended? Again depends on the area.
CC or App pay systems is a perfect fit in urban areas. Especially near colleges and universities. Rural or low income, not so much. You have to understand your business and customers before you implement changes. Some areas and demographics are not used to or very slow in embracing those types of changes.
Can it be done? Of course, absolutely but understand your market. You cannot force a pay system on somebody or on a location where that is something that they are not accustomed to. Keep in mind that doing so can have negative results such as pushing your customers to a competitor that is not forcing the end user on how to pay or do the laundry the way that they have been doing it for years.
It’ll be process very much like when mats transitioned from top loaders to front loaders. Similar experiences and reactions.