Two consideration here, apart from whether to use a deck with digital out or not.
Firstly, DAT tapes can play fine on one machine and not play at all on another. You might find that the tapes will only work reliably on the machine they were recorded on, in which case you've got to go with whatever output it happens to have.
Secondly, DAT tapes are pretty delicate things, and if you decide to play them in a machine other than the one you were asked to use, and that machine eats the tapes, you may find yourself in an embarrassing position. In any event it might be worth saying to the tape owners that while you will take every care with their media, you won't accept liability for any damage which may result in attempting to play them. And ask before playing them on another device.