Verranzano will have cars but they'll be moving along at midnight on Friday night. LI traffic? Depends what you mean by Friday night. 3:00 PM until 8 PM will be a standstill at times, again also depends on where on the island you are. There are only 3 major roads, The Northern State Pkwy., LI Expressway and Southern State Pkwy. Large commercial vehicles are only allowed on the L.I.E. (495).
If you post where your destination is I can probably be much more precise in plotting a route for you. There are certain roads you want to avoid at certain times (strip malls, industrial parks, etc.). If you're heading out to the east end of L.I. you can probably avoid the tunnels all together.