i have found a way to get photos uploaded from eye-fi card to an iPad to be recognized by PHOTOSTREAM, and thus appear on the other devices that utilize the same photostream account. I think the problem is the way that eye-fi adds the photos to the PHOTO app on the iPad - iPad doesn't seem to recognize that a new photo has been added for photostream's purposes. What needs to be done is the iPad Photo library needs to be updated to reflect any changes, additions, or deletions to the library.
This can be done using the iPhoto app from apple. Once you access this app, it "updates" the iPad photo library, and immediately, the photos added to the iPad photo library show in PHOTOSTREAM! You just have to purchase the iPhoto app from apple in order for this to work.