I agree that adults and peds are very different areas. But I would not agree that "if you can care for a child, you can easily care for an adult." As you said, they are very different.
It seems like (in my opinion) you have already convinced yourself that Johns Hopkins is the best place for you to work and that you are trying to find someone to talk you out of it.
One of the facilities in my area pays dayshift float pool RNs (Critical Care, Med-Surg, and Telemetry) $40/hr for days and $45/hr for nights. Weekend diff is $4 per hour. No benefits with the float pool positions. Regular permanent positions for new grads start at between $21 and $22/hr.