Milan Seven Days

Depending on your interests, you can do day trips to Monza, Pavia, Bergamo, the Lakes Region, Verona, and Turin.

You can learn about what to do/see in Milan and day trips on this website: https://www.yesmilano.it/en

Milan has the duomo and the Galleria, to start with. I'm going to Milan this Friday, but have only one day, so this trip I have tickets to the Last Supper. From there I am taking the train to Verona. Combining history and music, while in Verona I am going to the opera at the arena there, since it's opera season. You could see Verona on a day trip. You could also see Lake Como on a day trip. Have a great trip.

Just search things to do in Milano
Last Supper - buy a guided tour

You can daytrip to Venice or Florence in two train hours.
Brescia is an hour away.

Milan has the Brera museum, that is in the world class category, and the Ambrosiana and Poldi Pezzoli, not as large and important but still displaying important collections. Teens may like the Museo della Scienza e della Tecnica and maybe the Sforza Castle. An easily overlooked church is San Bernardino alle Ossa, that being close to the ospital cemetery has a chapel decorated with skulls and skeleton - horror, but it is the real thing, not fake. The Duomo terraces are magical. The Leonardo Ultima cena is so difficult to get tickets for, but if you can't don't be overly sorry. Torino and Parma are quite close by train, but actually most of north Italy is close by train; even Florence is only two hours away.
Lakes are also close, and you can also have a trip to Switzerland (e.g. Lugano, bring your passports).

I never turn down a free stay! That science museum (mentioned in an earlier post) is at least a half-day visit. Enjoy!

hey hey danaholve
go for it, free stay sounds fabulous. lots of things to see and do. how old are your teens and what are your dates? stay in milan and do some day trips taking advantage of your "free" stay.
italyweloveyou.com
16 best things to do in milan. it is one of the fashion capitals, many churches and architecture, plazas, risotto dishes especially risotto milanese. milan area has many rice patty fields instead of pasta dishes. (milanoexplorer.com for rsetaurants)
museoauto.com
take a train to torino/turin. your kids maybe interested to see all the classic cars within museum.
italyweloveyou.com
15 best things to do around lake iseo. take a day trip to the lake or keep your milan place and do an overnight to lake iseo. your kids may love to stay at the lake for beach/water activities. beach/poolside resort in a mobile home to relax & enjoy
sassabanek.com or visitlakeiseo.info (beaches on the lake)
or go early and spend time on the water at the beach, look at taking a boat ride on the lake
getyourguide.com/ milan
a reseller of tours to see what is offered. scroll down to company that has them. book directly on their own website. some plazas (piazzas) may have a tourist kiosk with things to do also.
gpsmycity.com/ milan
self guided walking tours you download
tripsavvy.com/ milan and top neighborhoods to visit, foods to try
galleria vittorio emanuele, a city center of fashion and culture, mosaic floors, shops and restaurants. navigli area to take a ride on a canal boat, sit outside cafes for lunch or dinner.
roam around the town, window shop just enjoy with your kids. have a great trip
aloha

The cities I might pick have all been mentioned except Cremona. You said you like music, and Cremona is the home of Stradivari. There’s a wonderful violin museum, plus they have short concerts there during weekends. The cathedral has a gorgeous interior of beautiful frescoes lining the aisle, and the clock tower has a clock “museum” as you climb it.

I think Cremona is an hour from Milan.