can i put two kindle accounts on the same ipad

The Kindle app on the iPad can only be linked to one Amazon account at a time - and I think (though I'm not sure) that if you log out the currently logged in Amazon account and then log in with the second account, that the first account's content becomes locked and inaccessible.

You could try having the second account on their browser based cloud reader, which you can create a homescreen shortcut for in Safari and in which you can download and store books for offline reading : http://read.amazon.com