I think if you back them up to CD/DVD they will last longer than backing them up to a USB stick that may well got lost or stolen (or stop working) in that time.
Anyway, backing up important files to ONE place is VERY VERY risky and it is worth backing them up to multiple places just to be sure.
I would put them on CD/DVD (two copies), AND on an external hard drive, AND maybe on another family computer.
Note you can also upload them to "secure" web sites like Dropbox or SkyDrive from Microsoft. These are secure as you have to logon to be able to access the files and if you have the userid/password no one else can acess them or see them.
Dropbox and SkyDrive are not image viewing sites like Photobucket or Flickr, they are data storage areas, which is a totally different thing.
Not a good idea to upload them to facebook as it can reduce the quality and it is alsoways best to keep pictures at the best quality.