my friends and I were going to be together

[Sarah-Betty]

I’ve always had a thirst for adventure and often get itchy feet. I can say that I had the most amazing adventure many years ago, when a group of friends and I had a great chance to get away from the hustle and bustle of the city to explore some caves near an ancient village in the countryside. That was also the last summer when my friends and I were going to be together before heading off to university, so it was good to do something special, something memorable.

Source: It was written by a native teacher.

Is "that" dummy here?
Why did the author used the verb tense "be + going to"? Can we used "My friends and I would be together" instead of the whole bold part?

 

[emsr2d2]

"That" refers back to the summer when they went to explore the caves. Yes, "... my friends and I would be together" could be used instead.

 

[Tarheel]

Why did the author use the verb tense "be + going to"? Can we use "my friends and I would be together" instead of the whole bold part?

Please note corrections. (If you were rewriting that, "my friends and I would be together" would be a good replacement for the part in bold.)

 

[yi-ing]

Can we use "in which" instead of "when"?
That was also the last summer in which my friends and I were going to be together before heading off to university, so it was good to do something special, something memorable.

 

[Tarheel]

I don't like "in which" there. What's wrong with using "when"? (You could delete "when" altogether. Say: "That was the last summer my friends and I were going to be together....")