Ralph, you have two good questions here—one about teaching your daughters about privacy and appropriate limits with adults, and the other about bathing your girls.
First, this is a good time to start teaching your daughters about privacy and “stranger danger,” in a relaxed, non-scary way. It would be best to talk about this in a separate setting from bathing. When you’re in the car with them or in other ordinary places, like going for a walk or playing in the park, you can practice a few scenarios with them: “If someone drives up in a car and asks you to get in and help find a lost kitten, what would you do?” Emphasize that most people are good and do not hurt children, but it’s very important to know when to say, “No!” and when to run away and get help.
There are some excellent children’s books that deal with this topic, such as “My Body Is Private,” by Linda Walvoord Girard and Rodney Pate or “Your Body Belongs To You,” by Cornelia Maude Spelman and Teri Weidner.
As far as bathing, your daughters are getting to an age when they can probably do most of it themselves. They could even bathe together and help each other rinse off after shampooing. If your daughters want adult company, but you want to start giving them more independence and privacy, you could sit on a chair on the other side of the shower curtain or outside the bathroom door. You might also experiment with a comfortable seat for your wife in the bathroom. For the next couple of years you’ll probably see occasional glimpses of your daughters naked. As they get older and start entering puberty, they will naturally start covering up and closing doors to ensure their privacy.
For now, if you no longer feel comfortable bathing your daughters, it’s important to discuss this with your wife. There are many other things you can do around the house and other ways to continue to have close, loving time with your girls, such as taking them for walks, having them help you fold the laundry, playing cards together and reading to them before bed.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.