As new as you can get

[BleeckerSt_Girl]

You don't say how old you are, are you very out of shape, what kind of weather you live in , what's the terrain like, hilly/flat? All this effects what kind of bike is right for your situation. You are planning to use your bike for a lot of very different type activities- that might make choosing/finding a bike a bit hard if you want one bike to 'do it all'.
A used bike might work for you to start with- if it doesn't need lots of repair it might be a better quality bike than any $100 Walmart bike. A used bike will need to be looked over by a bike shop to make sure it is safe to ride (brakes, tires, cables etc).
I would also suggest that you get at least a little comfortable with riding again and read up about bike traffic safety before you try to pull your 2 year old child behind you on the road.
Good for you wanting to ride a bike again!