Thanks for your query.
Retraction pocket is fairly common and has been observed in about 25% of British children. Unless there is a cause for the retraction pocket I do not see any reason for surgery in the ear and would agree with the second opinion
that you got.
In case of moderate hearing loss
in the affected ear what has the doctor suggested. Will a hearing aid
help the child? In case it does than it is advisable to get a hearing aid.
Surgery by an ENT surgeon will depend on the surgeon's expertise in that field. In case the surgeon has been doing such type of surgeries frequently than the surgeon has gathered expertise over the years in it.
I hope I have answered your query to your satisfaction. Feel free to revert back for any clarifications that you have.
Wishing your son all the best...