I live in Newton, and I know that every Saturday if it's nice out there are a ton of yard sales. Although my mom does usually let me use the car, you could just take the T, hop off and walk around. A bike would probably make it easier, although lack of a car makes it hard to carry a bunch of stuff. It seems that a lot of churches and temples have yard sales. If you're interested, Temple Rayim on Washington St. in Newton is having a big yard sale June 6th.
I think that Two Jays Customs is a neat name because it is "mommy" oriented in that it is based off of your kids' names, but not as serious sounding as Designmark. I think it is a good medium between the varying things you are planning to do.