Some people have indeed activated their passes on their tablets.

I suppose, if the app works on the iPad, then it should be OK.

As long as you can connect the Ipad to the Internet at least every 3rd day and that you can access any reservations that you might have on your Ipad it should work.

This provided that, as @rvdborgt wrote, that the app works on the Ipad.

In theory, the app and mobile pass needs at least iOS 13.0 or later or Android 6.0 later to function optimally. Whether you use these operating systems on a smartphone or tablet should not matter. However, please note that the app was specifically designed for use on a smart phone, so functionality on a tablet will likely be less than ideal. 

Even though it will probably work it really is not a good idea.

You will have to get your ipad out at some stations, sometimes at crowded gatelines, for inspection, while also carrying your luggage. There is no way this isn’t going to be a higher risk for theft due to the awkwardness and distraction.

Either use mobile pass on phone or paper pass with paper travel diary would be my advice, and given the choice I would go for the paper pass.