Vision seduced a 16yo entrusted to his care

The only thing that says something about their age is Cap saying "Ah, come on, Tony. She's a kid."  But then Cap is almost 100 years old. 

Added in:

Age of Ultron says they were orphaned at 10.  I'm guessing that Stark bomb was before he became Iron Man.  So by AoU they had to be older than 17.  And that's just going by if their parents were killed the same time he became Iron Man.  But the character being 26 (her age at the time of AoU) tracks.