As you’re going to be in Italy in September you have to do the Monza GP, it is the first weekend in September though.
We did a great trip including the F1 last September, went to Bergamo after it which is a pretty impressive walled city, great food up in the walled section but worth noting a lot of the trains stop at 9pm and taxis seemed VERY scarce… We were staying on the outskirts of the city so was a long walk at 11pm
Aosta valley is also pretty nice and Pila bike park is open till the middle of the month, although taking an XC bike down the top to bottom red/black downhill track was a painful mistake in hindsight, not helped by the fact it was all 2 inch deep dust.
For semi-remote alpine lovelyness Cogne is also worth a visit, some great walking an MTB above the village and there is a particularly good pizzeria on the main square.