Of us going/doing somewhere/something..

[aachu]

Respected teachers, I cam across a sentence, "It's just a matter of us going out and doing it", keeping this in view can I say say, "It's a matter of my going out and doing it", or I'll have to say, "It's a matter of mine going out and doing it". I would also want to know which of the following are correct.

It's a matter of him/her going out...
It's a matter of his/hers going out
It's a matter of them going out..
It's a matter of their going out...

[5jj]

I came across a sentence, "It's just a matter of us going out and doing it", keeping this in view can I say say, "It's a matter of my going out and doing it",
Yes. Some people would use 'me'
or I'll do I have to say, "It's a matter of mine going out and doing it".
No. That is not acceptable.

It's a matter of him/her going out...
It's a matter of his/hers her going out
It's a matter of them going out..
It's a matter of their going out..