Plug your iPad into iTunes, right click on the device (listed on the left of iTunes) and click "transfer purchases" and also back up the iPad. The apps should show up under the "applications' tab right above your "devices tab" on the left of ITunes
I just tried this with two games and none of the data was saved. The only way I can think of saving data is to restore a backup in iTunes/iCloud, but that's unnecessary when I just want to save the data from one app.