Since you only have 8gb then you probably only could backup 2 games (if you are lucky, maybe 3).
Sorry but Im not sure you can backup your games to an sd card but you try using this tut:
http://lifehacker.com/5518518/how-to-back-up-and-play-your-wii-games-from-an-external-hard-drive
If you still want to use the sd card then I think it will work if you use this program on your computer:
Wii Backup Manager
I never tested it before so it might not work.
First: Open Wii Backup Manager
Second: Go to the drive tab
Third: There is a place named Inactive, click on it and change it to you sd card volume (F:,G

Fourth: It should say there is no wbfs folder and asks you to create one, click yes. (Make sure it is in fat format, formatting erases everything)
Wii backup loaders should now be able to use the sd card
I would try either usb loader gx or WiiFlow to backup your games.
All you have to do is put in you game into the wii
In USB Loader GX: Once you put in your game, it should prompt you to install the game
In WiiFlow: Go to settings (in WiiFlow) and go to the second page (I think). One of the options will say: Install Game from disk
There you go.
I really recommend that you use a usb. It is easier to use.
You should also install wads to your wii that act as channels. It will be better for kids to quickly open the channel (USB LOADER GX or WiiFLow)