1. OK
2. OK
She and our son ...
3. OK
4. comma needed
(I don't know of any skis that aren't expected to be parallel! Are you trying to differentiate between skiing with two parallel skis and snowboarding with one wide and short "ski."
5. I don't know the details of this. Sorry.
6. Both sentences are OK.
Example here:
http://books.google.com/books?id=Z1gEAAAAMBAJ&pg=PA35&lpg=PA35&dq=%22to+run+on+skis%22&source=bl&ots=J5-FZDgM6m&sig=5Z3h1D6ExPdZplN_F7cT2-94zUM&hl=en&sa=X&ei=7j7-TrKbL5S4twfO97WPAg&ved=0CDUQ6AEwAA#v=onepage&q=%22to%20run%20on%20skis%22&f=false