Hi,
For beginners or even intermediate students, translating articles may be too much of a reach. Seconding one of Andy's other ideas, they could easily add Arabic descriptions to Wikidata items. I see a lot of Wikidata items that lack descriptions in very many languages. This can also be a good exploratory exercise for Wikidata. How are their favorite movies, TV shows, authors, artists, represented? What about the place they are from? Institutions in their hometown? Seeing which of these have articles in Arabic and seeing what the difference between the English and Arabic language articles is could also be a good jumping off point for translation.
I'm assuming the other instructor is familiar with Arabic Wikipedia policies?
Keep us posted on what you and the students accomplish!
Merrilee