Hi Ellen!
My husband is a huge car guy, and we toured the Lamborghini Factory in 2011.
1) Book tour tickets ahead of time. You need to make your reservation - so choose a day and work it into your schedule. You can always email them through the website to check on availability and times if you are trying to decide between different days.
2) There is not a train connection to the Lambo factory. You can take a bus from Bologna, as we did. However, (story time) because the signs were small to read and we weren't sure of where to get off, my husband and I got off the bus a town too early. We were walk/running down the side of a highway, hot in September, as trucks with bales of hay were passing us on the highway. It was a scene out of a movie. We finally stopped at a gas station we reached, I asked the owner to call up a taxi and it took us the rest of the way. We arrived a little late for the tour but they brought us in and met us up with the group. Moral of the story: you may want to hire a car service to take you from Bologna, or rent a car if you'd rather do that. You can take a bus, but it gets a little tricky - and I would hate if you were late to your tour like we were, haha.
3) Enjoy the tour! You go through the factory, get to touch some of the leather they use for the seats, learn all about the process... It was a treat. The museum and shop at the end were cool, but the tour itself was really great. My husband and I grabbed lunch in the town (just walked down the road from the factory) afterward. While sitting outside eating our sandwiches, some employees of the factory were test-driving a Gallardo, so that was fun to watch! It's a tiny town - not much to see, but sometimes you get lucky with a glimpse of them testing cars.
If your son likes cars, he will adore the tour. The 40€ per person isn't cheap, but I think it's way worth it. My husband's description of the tour was "I'm like a fat kid in an all you can eat buffet specializing in sweet treats at this point..." We were lucky enough to be there on the day that the President of Lamborghini was present, and he was showing off the yet-unreleased Aventador to some Audi execs who were in town, so that is a great memory!
Feel free to message me if you have any questions. I think the suggestion above to rent a car to do the Lamborghini Factory and the Ferrari Museum is a good idea if you want to do both. Just remember the usual advice - have your IDP and be careful of ZTLs.