I am in Tel Aviv on a Tiyul with my family and see a Shawarma restaurant with Teudah from the Rabbanut Rashit of Tel Aviv. It is not Mehadrin though. Is it still acceptable?

ב"ה Shalom Sorry, I couldn't help you this time. The questions sent do not come to us directly. In any case, a Teuda given by the Rabbinate in Israel is reliable, however as you pointed out it this placec was not mehadrin. That may mean that the meat is not Glatt, and if you only eat Glatt then you should refrain from eating there. In addition, on every Teuda, the name and phone number of the Mashgiach are available and you can call him to verify specific information which concerns you. All the best