I'd say 38wks too. I've had babies in the 37-39wk range for medical reasons and my 39 has done best long term wealth wise. My 37wk guy even though he was ok at birth has had allergy issues, chronic ear infections, asthma, etc.
If your dr will do 38wks I think it's good compromise in your situation.
Kristi, Mommy to Josh & Nick (identical twins 6-97) Nathen (3-02), Joey (2-04), Jacob (11-05) & Aaron (12-11) I sell Tupperware!
"A person's a person, no matter how small..." Dr Seuss