Syncing issues with lost of iTunes account.

We have a house with 1 computer, 2x iPhones 4S, 1x iPad, 2xiPad mini's and 6x iTunes accounts (including 1 account we no longer use). When syncing the iPads an error message comes up saying some files can not be synced because iPads can only hold files from upto 5 iTunes accounts. how do we solve this issue? Can we close down the old account and keep the file from there? Any advice happily accepted.