I work near the western end of the GW Parkway (actually in Maryland, but you get the idea). Here are my thoughts regarding the Maryland suburbs:
Poolesville has very good schools. Still in MoCo. Long drive for your wife. Real estate is not too expensive out there. 45 minutes to the head of the GW parkway, so she would still have a ways to go to get to work. Poolesville has public water and septic.
Darnestown is closer in, somewhat more expensive, probably has good schools, but it will still take your wife 30 minutes to get to the GW Parkway. Most of Darnestown does not have public septic - you will have a tank.
I have a coworker who hates MoCo, who lives a few miles southwest of Frederick MD, still in Frederick County. He loves it there, but to me his commute is insane. Good school and cheaper homes. 45 minutes to the GW Parkway if 270 is clear, but that is a rarity.
Another coworker lives in Crofton, in AA County. His wife works as a teacher in that school system. His commute is wretched. I have urged him to explore whether his wife can transfer to work for the MoCo schools so they could move to Darnestown.
Generally I like any area west of I-270. Multiple back road routes are available to get to/from 270/495, very safe neighborhoods and the area in general is attractive. The further west and north, the cheaper.