I've lived in Sterling for 6 years and moved here from a small city out of state. There are lots of resources, but they are definitely spread out. If you're a 1 car family and want the Metro, I would lean toward Falls Church, which has some older areas but lots of character, and a farmers market by the town hall. I think the COL is a little less there but it's right next to McLean/Tysons so you have the shopping within 20 min. As a SAHM you can time your shopping for weekdays and non-busy times (non-weekends).
I get lost every time I go to Reston, and it seems to be more of a gourmet community, so I'm happy to have it as a nearby resource, but I choose not to live there. If you want a historic "small town" with a (small) farmers market and local eateries and stuff, I would choose Leesburg, but it depends on what resources you want, as well as how long your commute would be. DH did not want to live down the I66 corridor b/c it has terrible traffic for many hours per day.
There are a lot of parks, etc. that anyone can make use of. I love Sterling, but it's not really a walking community. If I wanted a walking type community I would choose Vienna or Falls Church, or Leesburg. With kids taking classes all over NOVA, we have lessons in Ashburn and in Merrifield (between Falls Church and Fairfax), and my daughter's orchestra has performances in Alexandria, Great Falls, and other places. There are active groups of Freecycle, LLL, Holistic Moms, etc. all over this area, and the NOVA families for natural living yahoo group is a great resource.
The libraries have lots and lots of free resources. If you homeschool, there are several peer groups. If you want alternative education, don't live in Sterling; there are better sounding options near Vienna, McLean, Arlington, etc.
There are lots of farm co-ops and delivery locations, including from Polyface Farms in this area, which is like the grandfather grass fed animals farm! I picked up milk, vegetables, ground beef, and natural bologna from my pickup location yesterday 10 minutes away. There are about 3 other locations within 20 min of my house. I forgot eggs, but I get them from that farm as well. Will have to check out the other tribe. :)