[DS] Mixed units?

Can you "mix" units in DS.

For instance, I have a unit of light tanks escorting
4 Supply trucks.  Can I make them one "unit" so
the move at the same time?  If I can may the LAD
on the tanks "cover" the trucks?

I'm still thinking Hammer's Slammers here.  In one of the
stories the tanks LAD is being used to cover the
dug in position of local infantry.  Could this be done
in DS without buying a dedicated air defense vehicle?