We went last year - just me and DP. We loved it!
But thing I would change is time of year - it was way too hot when we went. Middle of August. Bloody awful heat.
We did 4 nights. We did pretty much all the tourist stuff - lots of walking!!! Easily 25k steps a day. Our kids wouldn’t have managed the heat or the walking
Only thing we didn’t do was the buggy cart tour which I would absolutely recommend you to do! You will see a lot and it will then give you the focus on anything else you might want to explore on foot further. Definitely book this for your first day.
We had no issue with pickpockets - I wore a backpack with all our bits for the day and a separate bumbag with cards and phone in - which after being on lots of social media groups were what was recommended. Also a lanyard for my phone when I had it out.
It’s definitely location for the hotel - try to go central. We stayed at a hotel just on the city wall.
Theres water fountains everywhere - we just bought a normal big plastic bottle of water from the airport on the way and used it the entire time we were there
Restaurants - we found the best were on the outskirts of the city. We had one night eating at a tourist trap restaurant and not only was it horrendously expensive but it was shit.
Vatican - don’t panic too much about what you’re wearing. Shoulders and knees need to be covered but literally ANY outfit that fits this criteria is fine - short sleeve long dress for example. Also - Vatican was the only thing I was slightly disappointed with though DP loved - just felt like a massive museum tbh.
Also - try to plan your days. We did and had tours booked but we also wish we had just stayed an extra day - a day where we weren’t rushing about trying to see everything.