How many photos can 64G hold?
about 17,000 but that is only if you don't store anything else in there. Usually your data will be a mix of music, photos, videos, and other stuff.
A 64g IPad will hold up to around 58g of music, if you are not using it for anything else. A 64g IPad is enough to store over 5000 songs, but it would take up a lot of the IPads memory. Basically you can hold around 7000 songs depending on their length. However, you should be fine with a 16g IPad for they still hold a lot of songs.