Yep, both fine.
Johnathan's suggestions are also good, and a little more casual.
One thing I just want to mention though, the "Who are these people, guys?" could technically be interpreted two ways:
a) Hey guys, who are these people? (asking the guys who the people are)
b) Who are these people? Are they guys? (asking who the people are, and if they're male)
From the context, a native speaker will almost certainly interpret it as option 'a)', but the grammar is also correct for 'b)'.