what you can do is add that folder to garageband directory using ifunbox. here is the step:
- Open your ifunbox then go to "user Applications" on your left panel, then select garageband folder. You will see a folder as below:-
copy the folder you like to put into your ipad by copy it into "Documents" folder. and then quit the ifunbox and restart your itunes again and sync your ipad again and check if you can see the folder on your file sharing under apps tab. Wish you good luck.