I live in MD and want to go smallmouth fishing this fall up north maybe champlain, erie or somewhere else.  What are some good lakes to go to for a weekend trip

and how late into the fall is still productive.

You've got about a month left on Champlain assuming we get normal temps.

I hear the fall spinnerbait bite is insane in the fall at Champlain. Do they stay shallow until mid-October?

Right now there are a few fish shallow, but we were getting our bigun's last weekend on humps in about 14' of water. 

However yes they come in shallow until around Halloween.  Spinnerbaits, Flukes (PLEASE try the double Fluke rig, you will thank me),  Perch X-Raps, and bright cranks all produce right now.