We moved to Italy 3 years ago with our-then 5 month old and our 3.5 year old, and we've done a ton of traveling with them over the last 3 years. By far the hardest part is the transatlantic flight. We've made that trip about twice a year, and if you're prepared for it, you should do fine. Forget about packing light-- it's just not going to happen with a toddler-- instead, pack as many new (to them) and interesting toys and games to keep them occupied for the long flight. It takes a lot of parental involvement, and sadly you can't just nap for a few hours like you'd like to do, especially if the baby's not too interested in napping. Someone else mentioned the pacifier being your best friend. Yes, by all means use it. Start now if you haven't already :-) OK, only kidding a little. Up until our fairly recent weaning, that was our "go to" tool when all else failed. Anyway, you know your child and his personality, so you'll have a better idea of what it takes to keep him occupied for long stretches.
Once you're in Italy, things get much easier. People love babies and young children here. Lots of times the waitstaff will entertain the kids during a meal. Many pizzerias will give you a hunk of dough to play with. People help me get off the train with a stroller.
Another tip: you might consider not adjusting too much to the local time once you get here. People tend to wake up late and eat late throughout the day. You're not going to find many non-touristy restaurants open before 7, and most Italians start thinking about dinner around 9. If you're able to recalibrate your sleep schedule to align with the local eating time, it might be easier for everyone. And of course, you have to do as the locals do and take a LONG afternoon nap.
Anyway, it's not all a walk in the park, but Italy is one of the most child-friendly places on earth. Remember, he's not going to get much out of the trip-- find a way to enjoy it while he's along for the ride.