If you don't have one yet, anyone headed to Lighthousing in Michigan should buy the Penrose's book "Michigan Lighthouses" ISBN 0-723756-035.
Since you've seen the lights from Port Huron north, you've got just a few you could view around the Detroit area.
1. Grosse Ile (they pronounce it "gross eel")
2. William Livingstone Memorial Light on Belle Isle (they pronounse it "aisle")
3. Windmill Point a short distance from Belle Isle
4. Lake St. Clair (3 miles offshore)
5. St. Clair Flats Range Lights (said to be viewable from Mt. Clemens MI); a better view from Harsens Island (pronounced "eye-land"
) but that will involve a nice but longer side-trip including a short car-ferry ride.
6. Peche ("peach") Island Rear Range is in a park in 'downtown' Marine City.
I don't know if you can see the Detroit River Light from shore or not; Penrose doesn't say.
There is a 'new lighthouse' in the city of Monroe Michigan, but I don't have details on the exact location; I think it's in a city park along the Detroit River. Monroe is about 30 miles south of Grosse Isle.
You should be able to see all these lights on Saturday afternoon after picking up your car.
After leaving Marine City, you can double-back to get on M-59 West and get on I-75 North. Or you can take I-94 North to Port Huron, take I-69 West to Flint and pick up I-75 North there.
Of course if you choose the Port Huron route, you could revisit Huron Lightship and view Fort Gratiot.
Using Streets & Trips, and allowing 15 minute stops to view/photograph each lighthouse, it looks like you could leave Detroit Metro Airpart at noon and be at the Huron Lightship about 6:00 p.m. (assuming you don't go to Harsen's Island.)
I'll create a PDF of this itinerary this evening and add a link here. Anyone have information on viewing the Detroit River Light?