I want to add an other option. For kids at home, a bare SB-600 (or SB-700) can be enough.
Absolutely! If your walls are pure white, a bounced Speedlight can look great. However, if your walls are off-white, you'll have color casts.
If you don't have white walls, you can also buy a 4' x 4' sheet of white Foamcore from a photo supply, art supply, framing store, or possibly even FedEx/Kinko's locations. Foamcore actually comes in 4' x 8' sheets, but some retailers stock smaller, pre-cut sheets. If, not, buy a 4' x 8' sheet, and score it half yourself (problem is, this still won't fit in most passenger cars). You can also use styrofoam insulation sheets from Home Depot. Both materials are rigid, lightweight, and provide pure-white reflective surfaces, perfect for bouncing light. Just attach it to a stand, aim your Speedlight at it, and go!
Still, one of my favorite tools for quick and dirty (but gorgeous) portraits is a 60" umbrella. Yes, they spill light everywhere, but put a Speedlight-lit, 60" umbrella within a few feet of your subject, and voila! The umbrella itself isn't very expensive--most are under $50. All you'd need to complete the package is a light stand (e.g., Manfrotto), and any generic-brand, umbrella bracket with a cold-shoe mount for your Speedlight. Then, you'd have a very nice, very soft, very "professional" lighting tool, for only a few bucks.
Here's an example of a Nikon SB-800 mounted onto a 60" silver umbrella. The umbrella is just a few feet to the right of camera. The only other light used is a blue-gelled, SB-600, hitting the wall behind the model:
Nikon SB-800 w/60" silver umbrella + SB-600 w/blue gel.