How to move photos from an old eMac to an iPad?
I wound up giving PhotoSync a try. This had better (compared to GoodReader), if not entirely satisfying, results: I was able to transfer the photos (after exporting the photos from iPhoto on the eMac and copying them to an intermediate, newer Mac), and found that most had the correct date. But about 150 did not, these appeared as if taken today. I deleted them again for now. I suspect these failed because they don't have any EXIF dates set.

Next time I meet up with the eMac/iPad owner, I will try transferring the remaining 150 photos again after forcibly setting their EXIF date to the same date as the file's modification date. There's an answer on the Photography SE which details how to do that using the command line utility “exiftool”. I'll try to remember to report back here on whether this works. I’d still appreciate any answer explaining a more straightforward approach.

Edit: transferring the remaining 150 photos after forcing their EXIF dates was succesful. I'll summarize my approach for anyone wanting to follow it:


On the iPad, get PhotoSync from the App Store.
On an intermediate Mac, get the PhotoSync companion app from the Mac App Store.
On the intermediate Mac, install “exiftool” (I used MacPorts to do this).
In iPhoto on the eMac, use the “Export” option in the menu. Make sure to set the options to “Original”. Transfer the exported files to the intermediate Mac. Make sure to use a means of transfer that preserves the file modification dates.
Use the following Terminal command on the intermediate Mac to fix files without any EXIF dates by setting the EXIF “ModifyDate” to the file modification date:

exiftool -overwrite_original_in_place -preserve '-FileModifyDate&gt;ModifyDate' -if 'not $DateTimeOriginal' -if 'not $ModifyDate' -if 'not $CreateDate' *
Open PhotoSync on the iPad, and use the PhotoSync companion app on the intermediate Mac to transfer the files using the “Send” command in the menu.


Note that a drawback of this approach is that it doesn't preserve the organization of the photos into albums that was done on the eMac, but that was not an issue in my case.

Instead of PhotoSync, you may be able to use AirDrop to transfer the files, but I was not able to try this as I didn’t have access to a Mac which supports AirDrop to iOS devices.

Before fixing any files with exiftool, you may want to move the ones that need fixing to a separate subdirectory: exiftool -Directory=needs_fixing -if 'not $DateTimeOriginal' -if 'not $ModifyDate' -if 'not $CreateDate' *