Bologna,CinqueTerre,Milan. Just booked flights!

First, think about why you chose those places--interest of other posters might not overlap with yours at all. Make a list of what you want to see in each place, then how many days to give each should become clear. With day trips, you could definitely fill 13 days. You could also add another stop, it just depends on your interests.
Booking.com is great for accommodations.

I see you will have three couples traveling together. That makes me think you will want to have as few accommodation changes as possible just to make it easier on everyone--moving to a new location always takes longer than one may think.

If you want to see the Last Supper in Milan you will want to book tickets ASAP.

Bologna is a great location--both for seeing that city and as a base for day trips (via train) in the surrounding area. Bologna's tourism website is a good resource for that area. For Milan and the Cinque Terre area the Rick Steves guidebook will be helpful. Perhaps you can access copies through your local library.

Just a thought--since you have three couples and three desired destinations, maybe each couple can be in charge of the planning for one area? Even if it's just the hotel reservation and a list of possible activities, it really takes the pressure off one person being in charge of planning and gives everyone the chance to be an "expert" for a part of the trip.

Bologna will be an excellent base
From there you can day trip Ravenna, Padua, Ferrara, Venice, Verona, Parma, Modena… and more.

Do get your Last Supper tix asap, so worth it
From Milan can day trip to Lake Como or Maggiore, Bergamo is lovely…

I’d probably add a 4th stop-a few nights at one of the lakes. Stresa on Maggiore is very nice and easy to get to MXP from there.

Or I’d add a few nights in Venice at start or after Bologna

Last Supper official site
Our English tour for a few euros more was excellent
https://cenacolovinciano.vivaticket.it/eng?qubsq=f2a19eb7-424b-4c74-82b8-3ed5a65be541&qubsp=6e59a549-909e-4c1b-894a-3494f0955e14&qubsts=1675807199&qubsc=bestunion&qubse=vivaticketoperator&qubsrt=Safetynet&qubsh=bc5ef0bf9933d83a778bb5cf5c56664e

We stay in apartments in Bologna, but friends of ours who are experienced travelers with very good taste ( he is an architect, she is an import food buyer) really enjoyed their stay at Hotel Roma.

https://www.hotelroma.biz/en/

The location looks great.

If you would like to consider apartments ( separate small apartments in the same building), I can highly recommend a place we like. It would probably be lower in cost than 3 hotel rooms.

The apartments are located on Via Marsala at number 8 and 11. You can view 3 of them on Via Marsala on the Italian website:

https://studiovitaapartments.kross.travel/book/step1?adults=2&children=0&rooms=1&guests=2&n_guests=2&guests_rooms=2,0;&kross_lang=it&from=2023-04-18&to=2023-04-21&

But you could book more easily in booking.com. Look for Residence Ariosto by Studio Vita. The apartments at No. 8 and No. 11 are right across a small quiet street from one another. These 3 are the apartments that came up when I entered random dates in late April. Other dates will produce different results.

Edit: here are the links for Residenza Ariosto and the Dependence on booking.com, without dates, so it shows all the apartment types.

https://www.booking.com/hotel/it/residenza-ariosto.html

https://www.booking.com/hotel/it/residenza-ariosto-depandance.html

12 nights total?
6 nights in Bologna, 1 night at Cinque Terre, 5 nights in Milan or Como lake. Emilia-Romagna (BOlogna, Modena, Ferrara, Ravenna, Parma are all UNESCO World heritage places) and the lakes area around Milan (Como, Bergamo, Monza and so on) offer you much more than you think. Cinque Terre only a short nice view for relax and saying that you've been there.

Thank you everybody for your responses! We are cutting our time in Cinque Terre to spend more time in Bologna and Milan, would not be doing a great deal of hiking in CT because of the terrain.

Any specific vineyard recommendations in or close to CT?

and for Milan, would a day trip to Lake Como be a good option?

For Bologna, staying downtown has been recommended using bus as access to trains and all the sites. Food is fabulous there, I'm told. I hear the gelato at Gianni is a 'don't miss' - any other specifics for delish treats? was also told that Stanley Tucci has a TV show about Italian dishes by region. Anybody seen it/recommend?

thank you, happy travelers!