There is a woman that works with children that are retarded or have severe mental disabilities. Much of the care involves tending to the physical needs of children (whatever it might be.) In such a case is there still an issur negia by a boy that is 9 years old. Perhaps there is a heter since she is osek b’malachtah. Especially since it’s negia that’s not “b’derech chibah” and that this 9 yr old boy R”L has the mind of a 3 yr old. Perhaps there is room to be matir. Perhaps there are teshuva written about this or someone that speaks about it?
For a nine year old boy, one may certainly be lenient. As you note, the negi’ah is not a “negi’ah shel chibah,” and this is why it is permitted for a male doctor to take a woman’s pulse and so on (as the Shach writes, 195:20).
The teshuvah of Rav Moshe Feinstein concerning negi’ah on a crowded subway train is also well known, and indicates that in a situation where no chibah is involved, the touch is permitted.
The fact the child is retarded, which also distances the concerns to a great extent, should also be kept in mind.
Therefore, although for older boys there might be room for further discussion, for nine year olds I don’t see any room for stringency.