Lake Como, Lake Maggiore, Portofino and Cinque Terre, advice?

What kinds of stuff do you like to do? I'm a hiker, so I could easily split a week among Portofino and CT (I preferred the hiking in Portofino park, but a few days will give you time to get on the upper trails above CT). It will be easier to drop the car before CT (parking is scarce, and I don't think it's worth it to keep it parked in a lot in La Spezia for four days). Camogli and Santa Margarita Ligure are as nice as Portofino with much lower hotel prices.
Rather than two lake stops, I would consider some time in the Dolomites (or go stay in Switzerland or near the border) just for variety, but that's just my proclivity. Another idea would be to do lakes, Piemonte, then the coast--the best of all worlds.

not much into hiking at our age. need car to get from location to location.

Honestly, I'd look at places other than CT then. Not that you cannot enjoy it without hiking--plenty do, and about a dozen will likely jump in to contradict me right off--but if I were in your shoes, I'd rather go somewhere with fewer crowds if I were just into enjoying the view. There are alternatives that are better with a car (Tellaro is one I loved). I totally concur with not feeling the need to exclusively tour museums and churches, but if you are not hiking, you'll be watching a lot of coming and going--there is not a ton to do in the villages otherwise.
The parking situation needs to be looked into for both coastal spots. I am sure they charge an arm and a leg in Portofino for parking--they do for everything else! Though you don't need a car for the lakes (ferries and train), I have never heard it mentioned as a problem to have one in that area, but I would select hotels with that in mind just in case.

Hi, the islands on Lake Maggiore are very close to Stresa. Isola Bella is my favorite with the Borromeo Villa & formal tiered gardens. Isola Pescatori is next to it - a small fishing village with a few restaurants and a hotel. Isola Madre is near it and also has a garden on it. I’ve been to Stresa several times - a lovely location! I just travel by train, so I can’t give you info about the other towns on the lake. Villa Taranto, a few ferry stops from Isola Bella is also a beautiful garden.

Just one general comment - all of your locations have water. You might want to consider a little variety.

How do you all feel about staying in Portofino and taking day trip to Cinque Terre?

Is there a weeks worth of places to go if we stay in Portofino and use it as a home base after going to Lake Como and Lake Maggiori for week one?

Have you considered Santa Margherita Ligure rather than Portofino?

Never heard of it. What’s your recommendation?

I would never want to stay in Portofino unless you are a fan of high end shopping like Gucci. I think we spent two hours there and were very happy to leave, crowded. Pretty scenery but did not like it there.
We have enjoyed staying in Santa Margherita Ligure several times(very near Portofino,walkable ) Camogli is another very good choice nearby.Three days is fine for Santa Margherita but way too long for Portofino where two hrs is more than enough. Hotels in SML- Continental( directly on waterfront), , Grand Hotel Miramar, Metropole.
Lake Como- Villa d’Este is at the far southern part of lake and the scenic, most beautiful part of Lake Como with Alpine views is mid lake- look at Bellagio, Cadenabbia, Menaggio, Varenna. Hotel Serbelloni is the high end hotel in Bellagio. Hotel Tremezzo across the lake is well regarded too. We always rent apts there.
Lake Maggiore- It’s easy to take day trips to the islands from Stresa. Take a ferry to the north end of the lake which is in Switzerland if you like.
Four days is way too much time in the Cinque Terre. If you go there, stay at Hotel Porto Rocca in
Monterosso.