I have bought most of my smartphones on Craigslist.
You said to use for wifi only, and for kids use. So I guess you care less if the ESN is bad...
I prefer Craigslist over ebay...
Use alot of common sense from meeting up, inspection of phone to getting a good deal. I usually meet in public places like Starbucks. I ask most of my questions prior to meeting, first through email and then phone calls. I never accept to meet at a location they suggest...we both agree on a neutral place. I never meet if they change location at the last minute- even more so if I am in route. If you can bring along a friend do so. Don't carry your wallet, put it in the trunk. Put the money inside an envelope instead. Good luck.