What would a restaurant serve with the same meal?
Probably what you already are thinking.
Marinated Vegetable Salad would go well with the ziti and your already planned green salad and bread.
You need to consider what you can cook with the facilities you are using.
Another hot dish may not be possible under the circumstances. Only you know that.
For food safety, please be sure to remember .... keep hot foods hot, and cold food cold.