"I have to make the food, do the dishes and greet my relatives.All of that makes me really tired".
I found this sentence in some news article, but how those actions, "to make the food, do the dishes and greet my relatives" can be " all of that" instead of "all of those or these". Is it okay to say all of that in that situation?
'All of that' refers to the whole situation of preparing for your guests and welcoming them. 'All of these' would suggest that each of the three things you mentioned made you tired - possible, but unlikely.