To be certain, because I'm not certain after reading what's happing.
Go to the bottom of the Featured tab in the App Store on the iPad. Tap your Apple ID and sign out. Tap it again and sign in with the correct Apple ID.
Hold in mind that if you have apps on the iPad that were purchased using the old Apple ID, then you will not be able to update them using the new one.
It is possible to change your Apple ID user name, but only if it was not already an apple email address (@mac, @me, or @icloud). Changing to a new Apple email address results in a new account. Accounts can not be merged nor can purchases be transferred.