That would probably be too much, so I'm willing to let it go.
A faerie changeling is 2 to 4 feet tall and weighs 20 to 50 pounds?
Faerie changelings speak Common and Sylvan. Those who impersonate elven children also speak Elven?
That all sounds fine.
I think the descriptive text for the spell of forgetting might need changing to account for the fact that you don't run into these at the seelie court.
Human changelings as an underbar?