I wouldn't charge anything extra for walking a dog in my care during the day.
Bathing is something some Sitters just do as a courtesy if the client is with them long-term. Offering little things like this keeps them competitive.
What YOU choose to charge is up to you, personally. If you choose to provide those services as an add-on, determine what they are worth to you, in terms of your time and materials cost (dog shampoo, etc.), and client value. There are too many factors for someone else to determine for you, such as demand / value in your location, etc., that only you can determine.
All the best!
It depends on what you include with bathing. I would check your local groomers rates and go from there. I charge according to size and coat type and My basic bath inclides bath, brush out, nail trim and file, ears cleaning. I also give $5 off when they stay over a couple nights