I know in the past I've seen comments by nannies who have said they would refuse to give lessons w/out extra pay. Personally, if I'm going to spend 40 hours a week with my charges, I'd just as soon spend part of that time doing something I'm passionate about and sharing that passion! (I also chose to be a nanny because I wanted to be able to have an impact on children's lives, and knowing that my charges will have those skills and passion for the rest of their lives is what makes this job worth it for me.)
I am a swim teacher when I'm not nannying, and I love sharing that with my charges! We spent the summer poolside and now that it's cold out I try to get us to the indoor pool as often as possible. They are total beach bums and LOVE getting to swim. My goal is to have them all swimming independently by age 4. :) Their parents are thrilled (dad was a swimmer when he was younger) and pay the entrance fees to the pool for them and me. This summer I was in charge of getting everyone a swimsuit, sunglasses, etc, and keeping us stocked with swim diapers (I was reimbursed promptly for everything, and asked first if that was a task I'd like to take on). Recently I let them know that they all needed new waterproof shoes, and mb let me know a few days later that they had ordered them. I don't charge anything extra for this (but when I teach lessons, I make more than $5 over my hourly nanny rate).