My son will be turning 13 during our Italy trip. On his actual birthday we will be driving in Tuscany. We have the heart of Tuscany drive planned with stops at wineries. I know that this day is obviously not for him however that is the way the schedule worked. We are planning to take a boat tour and snorkel in CT for his birthday a few days later. Looking for some restaurant suggestions, unique restaurants along the Heart drive. He loves steak, baked potatoes, sweets. We are already eating at Taverna San Giuseppe. Is there a castle you can eat in?
If you are passing near Lucca, you can rent bicycles (and surrey bikes) and ride around the city atop the impressive walls. It's pedestrians and bikes only, so you can also let him enjoy going solo. Rentals at several locations, multiple vendors at Porta Santa Maria.
If you want a castle where to eat you can try here:
https://www.verrazzano.com/en/
But one of the best Florentine steaks in the Chianti area can be found here, in the town or Panzano nel Chianti:
https://www.dariocecchini.com/en/to-the-table/officina-della-bistecca/
If he loves steak, bistecca alla fiorentina is a natural!
Forget baked potatoes in Italy. As for steak, a good father should always remind children not to eat anything bigger than their head. This is especially true for Tuscan steaks. If you'll be near Siena, there's this https://www.visittuscany.com/en/attractions/adventure-park-of-saltalbero/ The Visit Tuscany website is a product of the Region of Tuscany and trustworthy.
Our son turned 11 when we went to Italy 2 years ago and he enjoyed gelato for 11 days! Simple but we took a photo each time and made a collage that he loves. We are going to Rome and the Amalfi Coast and I can bet he is already plotting. Enjoy your trip!