I also include a line that says we will be withholding taxes as required by the IRS and that nanny must be legal to work in the US.
I also require reliable transportation.
Really, you should think about anything that would be a deal-breaker for you and include that in the top section. Things that would be great, but not deal-breakers (a second language, ability to ice skate, likes to cook in my case) put in further down.