How much do you have to invest? You need a laptop with a wifi card, some Tshirts made, and a Sharpie marker.
'Cause it sounds like a good time to pick a charitable cause and gather some information. Get some brochures, stickers, etc. Then, sign up for a CPA offer that requires a full signup (name/address/zip/etc, no credit cards) and pays out well -- but it has to be a somewhat classy product -- makeup, for example. NOT acai or stop-smoking, but something with a gentlemans/ladies feel to it.
Get T-shirts made with the product's logo on the back and the charity's on the front (real small, on the breast-pocket area. Just black and white will do.
Pay for a booth in a mall for a weekend -- it's shopping season, so you're gonna hit some big crowds. Get all three of your teens wearing those shirts, directing people to sign up for a free sample of whatever classy product you're supporting. Tell them that you're gathering money for X charity, and that for everyone who signs up for the FREE SAMPLE, $x goes to the charity. (Don't tell them that you're keeping the other 90% of whatever you make.)
Have the kids hand out brochures for the charity that say "Thank you!" on them in Sharpie marker.
You can easily pull in an average of 30 signups per hour; if you make only $4 for yourself per signup, that's $120 per hour - $30 for the kids is $90 for you.
Granted, that's only on the weekends.
And yes, I got this idea from this forum, but I can't find the thread right now, or I'd link to it...I can tell you from experience that it works, though!