10" tablets would be way too big for a nursery setting - the weight of these tablets really make them very inconvenient to use in a busy setting. The iPods are on the other hand too small - the small form factor makes it difficult to complete an observation with media, text and EYFS assessments. A 7" tablet would be ideal - can be held in one hand (if you are carrying a child in the other!) and is not too small to be misplaced amid all the toys and other stuff lying around in the rooms.
Also check out eyLog (early years log - https://eylog.co.uk) - it is an Android based solution. The tablets can also be locked down completely to prevent any misuse (no FaceBook, e-mail, etc)