if you get a prompt to update your OmniFocus database, do not update. Your database will be converted to work only on OF3. If you leave it in the OF2 format, you can use OF2 on your iPad Mini and other devices running OF3. But you may not be able to use any new features that may require an updated database.
Thank you for your kind response. I accidentally did, in fact, upgrade my database to OF 3. Well, using OmniFocus on the iPad was nice while it lasted. :-)