I'm a MB with a 9 month old and 3 year old. Our nanny started with us when she was just 21 (she is now 24) and had been absolutely great! She was very mature, we got a great feeling watching her with our then 1 infant, she had a lot of experience and great references working a full time babysitting gig through college, plus she has interned in a NICU her senior year of college. I don't think you should base it on age. We were her first REAL nanny job, full time with benefits, but she has turned out to be an amazing hard working nanny whom my children love.
Defintiely check into her references well and watch how she is with the kiddos, but I don't think you're nuts
