Hi there,
Welcome to the country with the greatest hospitality I have ever seen!
Cats from Tunis to Sousse -- if that is the least of your worries sounds like you are doing fine! I have seen people carry just about anything on the louage. Granted it can be a little cramped. I would just suggest being willing to keep the kennels on your laps for the duration of the drive. You will need to ask special permission from your louage driver -- maybe an offer to pay for an extra spot on the louage. Similarly, you would have to sweet-talk the average taxi driver to allow the cats. On the train, I think they would be more sticky -- very likely have to put them on as extra luggage (not the safest for live animals) and pay the premium for that.
Have you traveled a lot in
Tunisia? Are you very familiar with the country? I lived there for a year and became quite accustomed to various regions. It should be noted that while there are many many stray cats all over the country, it is pretty abnormal (from what I saw) for people to keep a cat inside (as a pet). I just say this so that you can prepare yourself for questions and possibly comments from your neighbours. There isn't much of an SPCA type system in
Tunisia, so mangy, flee ridden cats sort of just have their run of the neighbourhood in most areas. You will find less of this in the tourist zone of Sousse, but as soon as you are in a residential area, you will notice that again.